fix(ui): simplify external object labels and star controls (#9929)

## Thinking Path

> - Paperclip is the open source control plane people use to manage AI
agents and their work
> - Operators rely on task detail properties and header actions to scan
linked resources and make quick decisions
> - External GitHub objects used a long pull-request label and repeated
mention counts that added visual noise without adding state
> - The task-detail star action also rendered as a labelled outline
button, unlike the compact star controls used elsewhere
> - These inconsistencies made dense task-detail surfaces slower to scan
and broke Paperclip's content-first visual language
> - This pull request shortens the GitHub pull-request label, removes
duplicate mention-count decoration, and aligns the detail star action
with the icon-only control pattern
> - The benefit is a calmer, more consistent task-detail experience with
accessible labels preserved for assistive technology

## Linked Issues or Issue Description

No matching public GitHub issue or open pull request was found.

**What happened?**

On the task detail surface, linked GitHub pull requests were labelled
`Github Pull Request` and could show a repeated `×N` mention count. The
detail-header star control used a labelled outline button rather than
the compact icon-only star pattern.

**Expected behavior**

Linked pull requests should use the concise `Github PR` label without
duplicate mention-count decoration, and the detail star action should
render as an accessible icon-only ghost button consistent with
neighboring controls.

**Steps to reproduce**

1. Open a task with a linked GitHub pull request mentioned more than
once.
2. Inspect the external-object property label and value row.
3. Inspect the star action in the task detail header.

**Paperclip version or commit:** `230126d80b` (`master` at preparation
time)

**Deployment / installation:** Local development, built from source.

**Scope:** Core UI; not adapter-specific, database-related, or
configuration-related.

## What Changed

- Render GitHub pull-request property labels as `Github PR`.
- Remove repeated external-object mention-count decoration from property
values.
- Render detail-header star controls as icon-only ghost buttons while
preserving `aria-label`, pressed, busy, error, and tooltip states.
- Expand component coverage for concise labels, duplicate-count
suppression, visual variants, and accessible star actions.

## Verification

- `pnpm --filter @paperclipai/ui exec vitest run
src/components/IssueProperties.test.tsx
src/components/StarToggle.test.tsx` — 54 tests passed.
- `pnpm --filter @paperclipai/ui typecheck` — passed.
- Visual review (before/after plus normal, starred, pending, and error
states):
45cb492185/star-toggle-review.html
- `pnpm check:token-gates` — reports five existing `#9627` violations in
files unchanged by this PR; the same values are present on `master`.

## Risks

- Low risk: changes are limited to task-detail presentation and tests.
- The star action remains fully accessible through its existing ARIA
label and tooltip, but it no longer displays visible text.
- External-object mention counts remain available in data; only the
redundant property-row decoration is removed.

> For core feature work, check [`ROADMAP.md`](ROADMAP.md) first and
discuss it in `#dev` before opening the PR. Feature PRs that overlap
with planned core work may need to be redirected — check the roadmap
first. See `CONTRIBUTING.md`.

## Model Used

- OpenAI Codex, GPT-5.3 Codex, tool-enabled coding agent with repository
and shell access.

## Checklist

- [x] I have included a thinking path that traces from project context
to this change
- [x] I have specified the model used (with version and capability
details)
- [x] I have checked ROADMAP.md and confirmed this PR does not duplicate
planned core work
- [x] I have searched GitHub for duplicate or related PRs and linked
them above
- [x] I have either (a) linked existing issues with `Fixes: #` / `Closes
#` / `Refs #` OR (b) described the issue in-PR following the relevant
issue template
- [x] I have not referenced internal/instance-local Paperclip issues or
links (only public GitHub `#NNN` / `github.com/paperclipai/paperclip`
URLs)
- [x] My branch name describes the change (e.g. `docs/...`, `fix/...`)
and contains no internal Paperclip ticket id or instance-derived details
- [x] I have run tests locally and they pass
- [x] I have added or updated tests where applicable
- [x] I have updated relevant documentation to reflect my changes
- [x] I have considered and documented any risks above
- [x] All Paperclip CI gates are green
- [x] Greptile is 5/5 with no open P2s, recommendations, or follow-ups
- [x] I will address all Greptile and reviewer comments before
requesting merge

---------

Co-authored-by: Paperclip <noreply@paperclip.ing>

ui/src/components/IssueProperties.test.tsx

@@ -2394,7 +2394,7 @@ describe("IssueProperties", () => {
       inline: true,
       externalObjects: [
         {
-          mentionCount: 1,
+          mentionCount: 2,
           sourceLabels: ["Description"],
           pill: {
             providerKey: "github",
@@ -2411,7 +2411,7 @@ describe("IssueProperties", () => {
           group: {
             object: null,
             mentions: [],
-            mentionCount: 1,
+            mentionCount: 2,
             sourceLabels: ["Description"],
           },
         },
@@ -2463,7 +2463,9 @@ describe("IssueProperties", () => {
     });
     await flush();
 
-    expect(container.textContent).toContain("Github Pull Request");
+    expect(container.textContent).toContain("Github PR");
+    expect(container.textContent).not.toContain("Github Pull Request");
+    expect(container.textContent).not.toContain("×2");
     expect(container.textContent).toContain("Github Issue");
     expect(container.textContent).toContain("URL");
     expect(container.textContent).not.toContain("URL link");
@@ -2472,13 +2474,13 @@ describe("IssueProperties", () => {
     expect(container.textContent).toContain("Open");
     expect(container.textContent).not.toContain("External objects");
     const label = Array.from(container.querySelectorAll("span"))
-      .find((span) => span.textContent === "Github Pull Request");
+      .find((span) => span.textContent === "Github PR");
     expect(label?.querySelector("svg")).toBeTruthy();
     const pullRequestLink = Array.from(container.querySelectorAll("a"))
       .find((anchor) => anchor.getAttribute("href") === "https://github.com/acme/web/pull/241");
     expect(pullRequestLink?.textContent).toContain("PR 241 - Merged");
     expect(pullRequestLink?.textContent).not.toContain("acme/web#241");
-    expect(pullRequestLink?.textContent).not.toContain("Github Pull Request");
+    expect(pullRequestLink?.textContent).not.toContain("Github PR");
     expect(pullRequestLink?.querySelectorAll("svg")).toHaveLength(1);
     expect(pullRequestLink?.className).not.toContain("paperclip-mention-chip");
     expect(pullRequestLink?.className).not.toContain("rounded-full");

ui/src/components/StarToggle.test.tsx

@@ -92,15 +92,30 @@ describe("StarToggle", () => {
     expect(onToggle).not.toHaveBeenCalled();
   });
 
-  it("surfaces a retry affordance on error for the button variant", async () => {
+  it("surfaces an icon-only retry affordance on error for the detail variant", async () => {
     await render(<StarToggle starred size="button" error resourceName="Alpha" onToggle={() => {}} />);
     const btn = button();
-    expect(btn?.textContent).toContain("Retry star");
+    expect(btn?.textContent).toBe("");
+    expect(btn?.getAttribute("data-variant")).toBe("ghost");
     expect(btn?.getAttribute("title")).toBe("Couldn't save — retry");
   });
 
-  it("renders the labelled Star/Starred button variant", async () => {
+  it("renders the unstarred detail variant as an unfilled icon without an outline", async () => {
+    await render(<StarToggle starred={false} size="button" resourceName="Alpha" onToggle={() => {}} />);
+    const btn = button();
+    expect(btn?.textContent).toBe("");
+    expect(btn?.getAttribute("data-variant")).toBe("ghost");
+    expect(btn?.getAttribute("aria-label")).toBe("Star Alpha");
+    expect(btn?.querySelector("svg")?.getAttribute("class")).not.toContain("fill-amber-500");
+  });
+
+  it("renders the detail variant as a filled, icon-only star without an outline", async () => {
     await render(<StarToggle starred size="button" resourceName="Alpha" onToggle={() => {}} />);
-    expect(button()?.textContent).toContain("Starred");
+    const btn = button();
+    expect(btn?.textContent).toBe("");
+    expect(btn?.getAttribute("data-variant")).toBe("ghost");
+    expect(btn?.getAttribute("data-size")).toBe("icon-sm");
+    expect(btn?.getAttribute("aria-label")).toBe("Unstar Alpha");
+    expect(btn?.querySelector("svg")?.getAttribute("class")).toContain("fill-amber-500");
   });
 });

ui/src/components/StarToggle.tsx

@@ -14,7 +14,7 @@ export interface StarToggleProps {
   error?: boolean;
   /**
    * "row" — quiet icon-only control for sidebar and browse-list rows.
-   * "button" — labelled Star/Starred button for detail headers.
+   * "button" — always-visible icon-only control for detail headers.
    */
   size?: "row" | "button";
   /** Called with the desired next starred value. */
@@ -63,12 +63,11 @@ export function StarToggle({
   }
 
   if (size === "button") {
-    const label = pending ? "Saving..." : error ? "Retry star" : starred ? "Starred" : "Star";
     return (
       <Button
         type="button"
-        size="sm"
-        variant="outline"
+        size="icon-sm"
+        variant="ghost"
         aria-label={ariaLabel}
         aria-pressed={starred}
         aria-busy={pending ? "true" : undefined}
@@ -92,7 +91,6 @@ export function StarToggle({
             !pending && error && "text-red-500",
           )}
         />
-        <span>{label}</span>
       </Button>
     );
   }

ui/src/components/issue-properties/external-object-rows.tsx

@@ -32,7 +32,7 @@ function externalObjectRowDisplayKey(group: IssueExternalObjectGroup): string {
   const displayKey = pill.displayKey?.trim();
   if (displayKey) return displayKey;
   if (pill.providerKey === "github") {
-    if (pill.objectType === "pull_request") return "Github Pull Request";
+    if (pill.objectType === "pull_request") return "Github PR";
     if (pill.objectType === "issue") return "Github Issue";
   }
   return externalObjectDisplayLabel(pill.providerKey, pill.objectType);
@@ -101,7 +101,7 @@ function externalObjectPropertyTitle(group: IssueExternalObjectGroup): string {
 }
 
 function ExternalObjectPropertyValue({ group }: { group: IssueExternalObjectGroup }) {
-  const { pill, mentionCount } = group;
+  const { pill } = group;
   const statusLabel = externalObjectPropertyStatusLabel(group);
   const providerLabel = externalObjectProviderLabel(pill.providerKey);
   const typeLabel = externalObjectTypeLabel(pill.objectType);
@@ -116,9 +116,6 @@ function ExternalObjectPropertyValue({ group }: { group: IssueExternalObjectGrou
         label={`${providerLabel}: ${statusLabel}`}
       />
       <span className="min-w-0 truncate">{value}</span>
-      {mentionCount > 1 ? (
-        <span className="tabular-nums text-xs text-muted-foreground">×{mentionCount}</span>
-      ) : null}
     </>
   );
   const className = cn(