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).

scripts/test-server.js

@@ -51,13 +51,12 @@ const env = {
   // No suite may fetch LiteLLM's price list (reset-pricing syncs at once).
   AGENTHUB_PRICING_SYNC: "0",
   // Nor run the developer's real agy (it may update itself) or send their
-  // real Cursor, Grok, Kimi or OpenCode login for the quota.
+  // real Cursor or Kimi login for the quota.
   AGENTHUB_AGY_USAGE: "0",
   // Nor refresh (spend) a real Claude pool login: its refresh token is single use.
   DASHBOARD_POOL_REFRESH_MS: "0",
   XDG_CONFIG_HOME: tmuxDir,
   XDG_DATA_HOME: tmuxDir,
-  GROK_HOME: tmuxDir,
   KIMI_CODE_HOME: tmuxDir,
   DASHBOARD_PIPELINES_DIR: path.join(dir, "fixtures", "pipelines"),
   // Never this machine's server-mode S3 install: its system unit would become