feat(ai-tools): drop OpenCode and Grok Build

- opencode.json / grok.json leave the built-in catalog; opencode-usage.js,
  its poller, transcript branch and table creation go with it (existing
  tables and session rows stay as history).
- A Grok payload reaching the Claude hook route (Grok runs the Claude hooks
  itself) is dropped instead of recorded as tool = 'grok'.
- quota.js no longer reads Grok or OpenCode Go logins.
- Redone on v2.8.22 from c6b2892 (feat/grok-usage, never merged).

server/README.md

@@ -655,23 +655,12 @@ An `antigravity` workspace carries no pipeline either.
   what it said so far; `GET /api/sessions/:id/transcript(s)` reads an omp
   session's journals from there. Under S3 each member's `~/.omp` is read only
   through `openSafeAsync`.
-- **OpenCode sessions:** `server/lib/opencode-usage.js` reads OpenCode's
-  SQLite store (`~/.local/share/opencode/opencode.db`, under `XDG_DATA_HOME`
-  when set) every `DASHBOARD_OPENCODE_POLL_MS` ms (default 15000, `0`
-  disables), when its file or WAL changed: each root `session` row becomes a
-  `sessions` row (`tool = 'opencode'`), its tree's assistant `message` tokens
-  per `modelID` become `token_usage` (reasoning counted as output), and each
-  child session (the `task` tool's) an `opencode-<id>` subagent row.
-  `opencode_stores` holds each store's mtime and `opencode_sessions` each root
-  session's newest `time_updated`; the transcript routes read the conversation
-  (messages + parts) from the store itself. A member's store and WAL are copied
-  through the guard before they are opened.
-- **Grok sessions:** Grok runs the hooks in `~/.claude/settings.json` (its
-  Claude compatibility), so AgentHub's own hook reaches `POST /api/hooks/event`
-  with no `tool`; `routes/hooks.js` tells it apart by the camelCase keys only
-  Grok sends (`hookEventName` + `workspaceRoot`), records it as `tool = 'grok'`
-  and drops its `transcript_path` (Grok's file, never parsed as a Claude
-  transcript). No tokens: Grok's session files are not read.
+- **Grok hooks:** Grok is not an AgentHub tool, but it runs the hooks in
+  `~/.claude/settings.json` (its Claude compatibility), so AgentHub's own hook
+  can still reach `POST /api/hooks/event` with no `tool`; `routes/hooks.js`
+  tells it apart by the camelCase keys only Grok sends (`hookEventName` +
+  `workspaceRoot`) and drops it, rather than record a Claude session whose
+  `transcript_path` is Grok's file.
 - **Quiet sessions:** agy fires no exit hook, so a session quiet for ten
   minutes (with hook events) or two (without) is settled to `completed`, its
   agents too, and sets its workspace idle. That workspace must be one the hooks left