feat(cc-config): list a plugin's skills, agents and commands by name

A plugin card showed "7 skills, 5 agents" and nothing more — the counts
were the whole story, so finding out WHICH skills a plugin ships meant
opening its install directory by hand. The contribution chips are now
buttons: clicking one expands a list naming each artifact with its
description, one surface open at a time. Commands render with their
slash. Hooks stay a plain chip — a plugin's hooks are matcher/command
pairs declared inline in plugin.json, not named artifacts.

`contributes.items` carries the four surfaces server-side; the existing
counts keep their type and are now derived from those lists, so a chip
reading "3 commands" can never sit beside a list holding two.

That also fixes a real blind spot. Each surface was read only from the
conventional install subdirectory, but plugin.json may declare its own
paths — this repo's own `ccam` lists three files under
plugins/ccam/commands/ and keeps commands/ empty, so it reported zero
commands. Both sources are now read and de-duplicated. A declared path
resolving outside the plugin's install directory is dropped: a manifest
is third-party data and must not turn the dashboard into an arbitrary
file reader.

Also pins the Refresh button's width: both labels share one grid cell so
the button is always as wide as "Refreshing…" / "Đang làm mới…" and no
longer resizes the toolbar when the state flips. Measuring the longest
real string beats a min-width that would be wrong in the next language.

Verified: npm run test:server (1370 tests, +6 for the new discovery),
npm run test:client (457, +3 for the expand behaviour), tsc --noEmit,
prettier and check-headers clean. Docs synced: docs/API.md, openapi.yaml
(new CcConfigPluginItem schema), ARCHITECTURE.md, docs/PLUGINS.md.

docs/PLUGINS.md

@@ -462,7 +462,7 @@ These plugins query the Agent Monitor API at `http://localhost:4820`. Key data s
 Rule types: `token_threshold` (`{ total_tokens }` — the spend-relevant guardrail), `event_pattern`, `inactivity`, `status_duration`.
 
 ### Config Explorer (`/api/cc-config/*`)
-Read every Claude Code surface (skills, agents, commands, output-styles, plugins, marketplaces, mcp, hooks, settings, keybindings, statusline, memory). `memory` includes the per-project file-based store with `scope: "auto-memory"` (carrying `project`, `name`, `isIndex`, `frontmatter`); those files plus `CLAUDE.md` are mutable via `PUT`/`DELETE /api/cc-config/file` with always-on timestamped backups. The page also **manages plugins and marketplaces**: paste a GitHub `owner/repo`, URL or local path to register a marketplace, then install / enable / disable / update / uninstall its plugins — each button runs the corresponding `claude plugin …` command on the dashboard host (argv array, never a shell string). Hooks and `settings.json` keys are editable per layer (user / project / project-local) through `PATCH /api/cc-config/settings`, a per-key merge that leaves every untouched key — including redacted secrets — exactly as it was.
+Read every Claude Code surface (skills, agents, commands, output-styles, plugins, marketplaces, mcp, hooks, settings, keybindings, statusline, memory). A plugin card's contribution chips are clickable: each one expands to name the skills / subagents / commands / output styles that plugin ships (from `contributes.items`), so the plugin's contents are readable without opening its install directory. `memory` includes the per-project file-based store with `scope: "auto-memory"` (carrying `project`, `name`, `isIndex`, `frontmatter`); those files plus `CLAUDE.md` are mutable via `PUT`/`DELETE /api/cc-config/file` with always-on timestamped backups. The page also **manages plugins and marketplaces**: paste a GitHub `owner/repo`, URL or local path to register a marketplace, then install / enable / disable / update / uninstall its plugins — each button runs the corresponding `claude plugin …` command on the dashboard host (argv array, never a shell string). Hooks and `settings.json` keys are editable per layer (user / project / project-local) through `PATCH /api/cc-config/settings`, a per-key merge that leaves every untouched key — including redacted secrets — exactly as it was.
 
 ## Plugin Development