feat(skills): curated GitHub catalog redesign (#3016)

* feat(skills): remove ClawHub catalog integration

Drop the ClawHub registry as a skills catalog source across web server,
shared UI, VS Code, docs, and locales. The catalog now serves git-based
sources only: the curated Anthropic repo and user-defined repositories.
Also removes the now-unused adm-zip dependency.

* feat(skills): redesign catalog around curated GitHub repositories

Replace the single-source dropdown with a card grid of curated GitHub
repositories (Anthropic, OpenAI, Cursor pstack/skills, Matt Pocock) plus
user-defined sources. Source cards show skill counts, GitHub stars, and
last-updated time; a global search covers all loaded sources.

Server: curated sources gain GitHub repo metadata (stars, pushed_at)
fetched best-effort with a 3-hour in-memory and on-disk cache; scans
run through a concurrency-limited, deduplicated cache with 3-hour TTL
persisted across restarts. Refresh still bypasses the cache.

Shared UI: source cards, global search with clear button, per-skill
GitHub links, install/installed states. VS Code curated list updated
to match. All new copy translated across 12 locales.

* fix(skills): address catalog review findings

- GitHub metadata fetch timeout drops to 1.5s (under the catalog
  client's 3s deadline) and failed lookups cache briefly (5 min) so
  repeated catalog loads do not re-hit a failing API.
- Disk cache files are written with owner-only permissions (0o600);
  rename preserves the mode.
- loadSource deduplicates concurrent in-flight requests per source and
  the shared isLoadingSource flag now clears only when the last active
  source load finishes.

packages/docs/content/docs/ja/skills-catalog.mdx

@@ -12,7 +12,7 @@ Skills Catalog では、自分で書く代わりに、他の人が公開した
 ## スキルをインストールする
 
 1. カタログを開きます。
-2. 組み込みソース（Anthropic skills repo と ClawHub community registry）を閲覧するか、検索します。
+2. 組み込みソース（Anthropic skills repo など）を閲覧するか、検索します。
 3. スキルを選び、インストールします。
 4. インストール先を選びます。すべての作業で使うか、現在のプロジェクトだけで使うかです。