feat(skill): extract the workspace-dependencies tool into a package

Move `load_workspace_dependencies` and the primary-runtime payload logic out
of `apps/desktop-host` into `@deepseek-ai/dsh-tool-workspace-dependencies`
so profiles other than Desktop can mount the same tool. Desktop keeps its
behavior through the package.

Two additions for carriers that are not Electron applications:

- `root` is optional: without it the payload is validated and used in place
  (no copy under the Harness home), which suits read-only container layers.
- `runtime.json` accepts `linux`, and the `node` / `pnpm` components are
  optional; the returned paths and the tool output omit what the payload
  does not ship.

The `sdk` profile mounts the tool and `@deepseek-ai/dsh-skill-office` when
`DSH_PRIMARY_RUNTIME` names a payload directory (its sibling `office-skills/`
carries the skill resources); both rows stay disabled otherwise. Both
packages join the Python runtime closure.

python/sdk-runtime/package.json

@@ -86,6 +86,8 @@
     "@deepseek-ai/dsh-shell-env": "workspace:^",
     "@deepseek-ai/dsh-skill": "workspace:^",
     "@deepseek-ai/dsh-skill-filesystem": "workspace:^",
+    "@deepseek-ai/dsh-skill-office": "workspace:^",
+    "@deepseek-ai/dsh-tool-workspace-dependencies": "workspace:^",
     "@deepseek-ai/dsh-spill": "workspace:^",
     "@deepseek-ai/dsh-subagent": "workspace:^",
     "@deepseek-ai/dsh-subagent-acp": "workspace:^",