FN-5904: feat(FN-5904): add browse-and-install flow for skills.sh catalog in Skills view

Add end-to-end browse-and-install flow for skills.sh catalog entries in the dashboard Skills view, enabling users to install skills directly from the catalog UI.

- Add POST /api/skills/install route with source validation and scoped project cwd
- Add installSkill method to SkillsAdapter using supervised npx skills add spawn
- Add installSkill client API function and Install button on catalog cards
- Refresh discovered skills list automatically after successful install
- Handle install errors with structured error codes (invalid_source, install_failed, install_timeout, spawn_error)
- Add card header layout with install button, disabled state, and loading spinner
- Add comprehensive tests: adapter unit tests, route integration tests, component tests
- Add changeset for @runfusion/fusion minor bump
- Update dashboard-guide.md with install endpoint documentation

Files changed:
 .changeset/four-oranges-film.md                    |   5 +
 docs/dashboard-guide.md                            |  45 +++++++
 packages/dashboard/app/__tests__/api-skills.test.ts |  46 +++++++
 packages/dashboard/app/api/legacy.ts               |  12 ++
 packages/dashboard/app/components/SkillsView.css   |  16 +++
 packages/dashboard/app/components/SkillsView.tsx   |  83 +++++++++---
 packages/dashboard/app/components/__tests__/SkillsView.test.tsx |  72 +++++++++++
 packages/dashboard/src/__tests__/routes-skills.test.ts |  67 ++++++++++
 packages/dashboard/src/__tests__/skills-adapter.test.ts | 113 ++++++++++++++++
 packages/dashboard/src/routes/__tests__/register-agent-skills-routes.test.ts | 144 +++++++++++++++++++++
 packages/dashboard/src/routes/register-agent-skills-routes.ts |  51 ++++++++
 packages/dashboard/src/skills-adapter.ts           | 103 +++++++++++++++
 12 files changed, 736 insertions(+), 21 deletions(-)

Fusion-Task-Id: FN-5904

Fusion-Task-Lineage: 338d53e3-baba-4c6c-9173-8e214242403c

docs/dashboard-guide.md

@@ -756,6 +756,8 @@ For setup prerequisites, security caveats for tokenized URLs/QR links, and troub
 
 ## Skills API
 
+The Skills view now supports the full browse-and-install loop for skills.sh entries: use **Skills Catalog** to search the catalog, click **Install** on any card with a source repository, and the dashboard will run the same installer as the CLI (`npx skills add <owner/repo> -y -a pi`, with `--skill <slug>` when applicable). On success, the view refreshes **Discovered Skills** immediately so the newly installed skill appears without a page reload.
+
 The Skills API provides endpoints for managing execution skills. Skills are toggled via project-scoped settings in `.fusion/settings.json`.
 
 ![Skills view](./screenshots/skills-view.png)
@@ -871,6 +873,49 @@ Toggle a skill's enabled/disabled state.
   { "error": "Skills adapter not configured", "code": "adapter_not_configured" }
   ```
 
+### POST /api/skills/install
+
+Install a catalog skill into the current project.
+
+**Request Body:**
+```json
+{
+  "source": "owner/repo",
+  "skill": "example-skill"
+}
+```
+
+**Behavior:**
+- Validates `source` in `owner/repo` format before spawning anything
+- Runs `npx skills add <source> -y -a pi`
+- Appends `--skill <skill>` when `skill` is provided
+- Uses the scoped project root as `cwd`, so installed files land in the current project's skill directories
+
+**Response:** `200 OK`
+```json
+{
+  "success": true
+}
+```
+
+**Error Responses:**
+- `400 Bad Request` — missing source
+  ```json
+  { "error": "source is required", "code": "invalid_body" }
+  ```
+- `400 Bad Request` — malformed source
+  ```json
+  { "error": "Invalid source format. Use owner/repo.", "code": "invalid_source" }
+  ```
+- `404 Not Found` — adapter not configured
+  ```json
+  { "error": "Skills adapter not configured", "code": "adapter_not_configured" }
+  ```
+- `502 Bad Gateway` — installer failed/timed out/could not start
+  ```json
+  { "error": "installer failed", "code": "install_failed" }
+  ```
+
 ### GET /api/skills/catalog
 
 Fetch the skills.sh catalog with optional authentication.