feat(ai-tools): install/update AI CLIs, remote catalog sync, cached favicons (#40 A2)

server/data/ai-tools/README.md

@@ -6,6 +6,24 @@ One JSON file per AI coding CLI AgentHub can run in a lane. Loaded by
 `DASHBOARD_AI_TOOLS_DIR` with the same `id` replaces the built-in one (it may
 not set `launcher`).
 
+## Install / update (A2)
+
+Two optional fields, honoured only in built-in files and in the copy of the
+newest release's catalog that `server/lib/ai-tools-sync.js` keeps in
+`<data dir>/runtime/ai-tools-remote/` — a file in `DASHBOARD_AI_TOOLS_DIR`
+carrying either is rejected, because an Install click would run what it names:
+
+- `install`: `{ "kind": "npm", "package": "<npm name>" }` (runs
+  `npm install -g <package>@latest` with the login shell's npm) or
+  `{ "kind": "script", "url": "https://…" }` (https, same site — last two host
+  labels — as `homepageUrl`; downloaded by the server, run as `bash <file>`).
+- `update`: `{ "kind": "npm" }` or `{ "kind": "script" }` (reuse `install`),
+  or `{ "kind": "self", "args": ["update"] }` (the tool's own updater).
+
+Before adding an npm package, check its owner (`npm view <pkg> maintainers
+repository.url`) and that its `bin` matches `detect`: a squatted name would
+install a stranger's code on every machine that clicks Install.
+
 ## Attribution
 
 The commands, prompt modes, permission-bypass flags and homepages of the tools