feat(adapter-claude): add Claude Opus 5 to the static model fallback (#10327)

## Thinking Path

> - Paperclip is the open source app people use to manage AI agents for
work
> - Agents pick their model from a dropdown in agent config, populated
per-adapter by `listAdapterModels()` → each adapter's live provider
catalog merged over a static fallback list
> - For `claude_local`, newer model ids only reach the dropdown via the
live Anthropic `/v1/models` fetch, which needs a server
`ANTHROPIC_API_KEY`, a <5s round-trip, non-Bedrock mode, and account
entitlement; on any miss it silently falls back to the static `models`
array
> - Claude Opus 5 (`claude-opus-5`) is generally available — Anthropic
lists it as the recommended model for complex agentic coding and
enterprise work — but it was absent from that static fallback, so it
appeared only when live discovery happened to succeed
> - This pull request adds `claude-opus-5` to the `claude_local` static
model list so it is selectable regardless of the live-discovery path
> - The benefit is a consistent, reliable dropdown that surfaces the
current GA Opus flagship without depending on a flaky live fetch

## Linked Issues or Issue Description

No public GitHub issue. The bug is described inline following the
bug-report template:

**What happened**
The `claude_local` agent-config model dropdown omitted Claude Opus 5.
`claude-opus-5` was missing from the adapter's static fallback `models`
array (`packages/adapters/claude-local/src/index.ts`), so it only
surfaced when the live Anthropic `/v1/models` discovery happened to
succeed.

**Expected behavior**
Claude Opus 5 is a shipped, generally-available flagship (Anthropic's
recommended model for agentic coding) and should always be selectable in
the dropdown, independent of whether live discovery succeeds.

**Steps to reproduce**
1. Run the server without a working live Anthropic `/v1/models` path (no
`ANTHROPIC_API_KEY`, Bedrock mode, a discovery timeout, or a cache
miss).
2. Open agent config for a `claude_local` agent and inspect the model
dropdown.
3. Observe that `claude-opus-5` is absent because the static fallback
list omitted it.

**Deployment mode**
Self-hosted / local adapter (`claude_local`); the server process reads
`ANTHROPIC_API_KEY` from its environment.

## What Changed

- Added `{ id: "claude-opus-5", label: "Claude Opus 5" }` to the
`claude_local` static `models` fallback. Placed after the current
5-family entries and above the legacy `claude-opus-4-7`, so
`claude-opus-4-8` stays the default (index 0) option.
- Added an explicit regression assertion in
`server/src/__tests__/adapter-models.test.ts` that `claude-opus-5` is
present in the `claude_local` fallback when live discovery is
unavailable.

## Verification

- `pnpm -C server exec vitest run src/__tests__/adapter-models.test.ts`
— **17/17 pass**, including the new `claude-opus-5` assertion and the
existing `models[0] === "claude-opus-4-8"` default invariant (unaffected
— Opus 5 is inserted lower in the list).
- Change is a single static-data addition plus a test assertion; no
control-flow change.

## Risks

- Low risk. Pure additive change to a fallback list; no control-flow
change. Worst case is an id a given account isn't entitled to, which the
existing "current"/manual-model UI paths already tolerate.
- Note for reviewers: a sibling PR adds `claude-sonnet-5` to the same
static array (near `claude-opus-4-8`). Both are complementary "refresh
the static list to current GA" changes; whichever merges second may need
a one-line merge resolution in
`packages/adapters/claude-local/src/index.ts` and the matching test
assertion block.

## Model Used

Claude (Anthropic), model id `claude-opus-4-8` (Opus 4.8), extended
thinking + tool use, run as the Paperclip CTO agent.

## 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)
- [ ] My branch name describes the change (branch is the assigned
execution-workspace branch and cannot be renamed this run)
- [x] I have run tests locally and they pass (server adapter-models
suite, 17/17)
- [x] I have added or updated tests where applicable (explicit
`claude-opus-5` fallback assertion)
- [x] I have updated relevant documentation to reflect my changes (n/a —
no docs reference this list)
- [x] I have considered and documented any risks above
- [ ] All Paperclip CI gates are green (pending CI)
- [ ] Greptile is 5/5 with no open P2s, recommendations, or follow-ups
(pending review)
- [x] I will address all Greptile and reviewer comments before
requesting merge

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

packages/adapters/claude-local/src/index.ts

@@ -9,6 +9,7 @@ export const models = [
   { id: "claude-opus-4-8", label: "Claude Opus 4.8" },
   { id: "claude-fable-5", label: "Claude Fable 5" },
   { id: "claude-mythos-5", label: "Claude Mythos 5" },
+  { id: "claude-opus-5", label: "Claude Opus 5" },
   { id: "claude-opus-4-7", label: "Claude Opus 4.7" },
   { id: "claude-opus-4-6", label: "Claude Opus 4.6" },
   { id: "claude-sonnet-4-6", label: "Claude Sonnet 4.6" },

server/src/__tests__/adapter-models.test.ts

@@ -67,6 +67,8 @@ describe("adapter model listing", () => {
     expect(models[0]?.id).toBe("claude-opus-4-8");
     expect(models.some((model) => model.id === "claude-fable-5")).toBe(true);
     expect(models.some((model) => model.id === "claude-mythos-5")).toBe(true);
+    // Opus 5 is a current GA flagship and must be offered even when live discovery is unavailable.
+    expect(models.some((model) => model.id === "claude-opus-5")).toBe(true);
     expect(fetchSpy).not.toHaveBeenCalled();
   });