feat: v2.5.5 — AI Router renamed AI Proxy, reload onto new builds, update no longer spins

AI Proxy (was AI Router):
- server/lib/ai-proxies.js, proxy-apply.js, routes/ai-proxies.js mounted at
  /api/ai-proxies and the old /api/ai-routers; `router` still accepted on the
  start routes; profiles move to <CLAUDE_HOME>/agenthub-proxies/
- dashboard_runs.router renamed in place to proxy: an older build on the same
  DB fails on that column, so dev and prod sharing one DB update together
- a proxy's baseUrl stored as its root (a typed /v1 made /v1/v1/messages);
  Test probes Claude /v1/messages and Codex /v1/responses
- Settings → AI Proxy (/settings/ai-router redirects), ProxyPicker

Updates:
- every tab reloads onto the new UI build when its WebSocket reconnects to a
  server of another version (lib/newBuildReload.ts, once per version)
- Update now stops waiting on a plugin chain that failed or pulled nothing
  (the old server never goes down), and reloads as soon as a new version answers

Also:
- a pane whose command exits at once says so (EPANEEXITED) instead of
  "Command failed: tmux set-option … mouse on"
- the pane drag preview draws where the pane actually lands

ARCHITECTURE.md

@@ -2296,8 +2296,8 @@ The same shape is used by `GET /status`, `POST /check`, and the `update_status`
 | Ahead of the newest release | `{update_available:false, dev_build:true, commits_ahead_of_release:N}` | Sidebar reads `Dev build · N ahead`; modal suppressed (a dev build is not an available update). |
 | Shallow clone (incl. the plugin cache) | `{shallow_clone:true, commits_behind_release:null, commits_ahead_of_release:null, dev_build:false}` | No commit badge is rendered at all — the numbers would be graft artefacts. Version compare still decides `update_available`. |
 | Newer release, ordinary checkout | `{update_available:true, situation:"release_available", latest_release:"vX.Y.Z", manual_command:"...git fetch origin --tags && git merge --ff-only vX.Y.Z..."}` | Modal opens titled with the release version, links its notes, and shows **Update now**. |
-| Newer release, plugin-cache install | `{update_available:true, situation:"plugin_managed", install_kind:"plugin", plugin_marketplace:"sg", plugin_name:"agenthub", manual_command:"claude plugin marketplace update sg && ..."}` | Modal opens WITH **Update now**; `POST /apply` answers `200 {applied:true, mode:"plugin"}` and the detached chain pulls the new version and re-bootstraps. The modal notes that an already-open Claude Code session still needs `/reload-plugins` for new skills/commands. |
-| Plugin chain ran but nothing was published | `{last_plugin_update:{ok:true, step:"already_current"}}` | The old server keeps running, untouched; no restart, no error banner. |
+| Newer release, plugin-cache install | `{update_available:true, situation:"plugin_managed", install_kind:"plugin", plugin_marketplace:"sg", plugin_name:"agenthub", manual_command:"claude plugin marketplace update sg && ..."}` | Modal opens WITH **Update now**; `POST /apply` answers `200 {applied:true, mode:"plugin"}` and the detached chain pulls the new version and re-bootstraps. The modal notes that an already-open Claude Code session still needs `/reload-plugins` for new skills/commands. It then polls `status` and reloads once the old server went down and answered again, or as soon as a different `local_version` answers; a verdict of this chain (`finished_at` after the click) that is `ok:false` or `already_current` ends the wait and shows it, since the old server then never goes down. Independently, every tab reloads itself onto the new UI build when its WebSocket reconnects to a server whose `/api/health` `version` is not the bundle's (`client/src/lib/newBuildReload.ts`, once per version). |
+| Plugin chain ran but nothing was published | `{last_plugin_update:{ok:true, step:"already_current"}}` | The old server keeps running, untouched; no restart, no error banner — a tab waiting on **Update now** stops waiting and says nothing new was pulled. |
 | Plugin chain mid-handover | `{last_plugin_update:{ok:true, step:"bootstrap", note:"the new plugin version is installed; the server is being handed over"}}` | Written BEFORE the handover on purpose: that step retires the process tree the helper hangs off, and a helper killed there would otherwise leave `last_plugin_update: null` for an update that succeeded. Overwritten by `done` when the helper survives. |
 | Plugin chain failed (no `claude` on PATH, `npm ci` broke, bootstrap died) | `{last_plugin_update:{ok:false, step:"resolve_claude"\|"plugin_update"\|"bootstrap", error:"..."}}` | Danger banner in the modal naming the failed step. A `bootstrap` failure means the old server was already stopped, so the verdict says to run `/agenthub-update` to recover — and it is read back by whichever server comes up next, because it lives outside the cache. |
 | Plugin `/apply` with nothing newer published | 409 `{reason:"plugin_managed", release_check:"ok"}` | No chain is spawned. Message names the newest release and points at `/agenthub-update` to force a refresh. |