Add Divoom watchface MCP skill.

Introduce a new skill that guides Claude to use mcp-divoom-lan safely with read-before-write guard rails, and include it in the example-skills marketplace bundle for easier discovery.

.claude-plugin/marketplace.json

@@ -31,6 +31,7 @@
         "./skills/brand-guidelines",
         "./skills/canvas-design",
         "./skills/doc-coauthoring",
+        "./skills/divoom-watchface-mcp",
         "./skills/frontend-design",
         "./skills/internal-comms",
         "./skills/mcp-builder",

skills/divoom-watchface-mcp/SKILL.md

@@ -0,0 +1,57 @@
+---
+name: divoom-watchface-mcp
+description: Use the mcp-divoom-lan MCP server to safely operate Divoom watchface workflows, including local read/patch, dial selection, brightness control, background replacement, and explicit local dial creation.
+---
+
+# Divoom Watchface MCP
+
+## When to Use This Skill
+
+Use this skill when users ask to control a Divoom watchface device via natural language, such as:
+
+- editing current watchface style or item values
+- switching active dials
+- adjusting brightness
+- replacing dial background
+- creating a new local dial
+
+## Preconditions
+
+- MCP server `divoom-lan` is installed and connected.
+- Device is reachable on LAN.
+- If target device is unclear, ask for host IP before writing.
+
+## Mandatory Operating Rules
+
+1. Use only `divoom-lan` MCP tools for runtime device actions (do not modify project code for operational requests).
+2. Always apply **read-before-write**:
+   - `watchface_get_local`
+   - inspect `ItemList`
+   - `watchface_patch_local` (minimal patch)
+   - `watchface_get_local` (verify)
+3. If `ItemList` is empty, stop patch flow and ask user to switch to an editable dial first (`watchface_set_clock_select`).
+4. Do not call `watchface_create_local_clock` unless user explicitly asks to create a new dial.
+5. For destructive operations (`watchface_reset_local_then_cloud`), require explicit confirmation.
+
+## Operation-Specific Guidance
+
+- **Brightness**
+  - Read current value via `watchface_get_brightness`.
+  - Apply via `watchface_set_brightness`.
+- **Background replacement**
+  - Use `watchface_replace_dial_bg_file` for background cache replacement.
+  - Use `watchface_upload_file` + `watchface_patch_local` only when config URL update is intended.
+- **Dial switch**
+  - Use `watchface_set_clock_select`, then read back to confirm expected clock context.
+
+## Response Style
+
+- Confirm the intended action in one sentence.
+- Execute one clear step at a time.
+- Return key result fields (`ReturnCode`, `ClockId`, `Brightness`, or patched fields).
+- If blocked, explain exactly what is missing and the next action.
+
+## References
+
+- MCP server repository: `https://github.com/DivoomDevelop/mcp-divoom-lan`
+- Visual editor (optional): `https://github.com/DivoomDevelop/divoom-watchface-visual-editor`