Let an AI agent see the open editor through MCP (#429)

Claude Code should be able to work inside the user's open editor tab.
This first stage connects the two and lets the agent look: what the
user sees and a picture of it. Changing the project comes in stage 2.

- An agent token per account opens only /mcp, no API route. The
  dialog "Agent tokens..." in the account menu creates it once, shows
  the ready "claude mcp add" line and revokes it. The server keeps
  only its sha256 (api/lib/AgentTokens.php).
- Wrong tokens count into the sign-in brake from #427. Changing the
  password, renaming or deleting an account ends its tokens.
- The relay (tools/mcp/) is a small Node service without packages,
  WebSocket server included. It runs in the container feuerwerk-mcp
  because PHP-FPM cannot hold connections. Whether a token or a tab
  ticket is valid is still decided by the PHP API, through two routes
  that answer only with the relay key.
- The tab joins over WebSocket on the same origin with the normal
  session, an Origin check and a one-time ticket. It connects only
  after "Agent" is switched on in the account menu. One tab per
  account is active, a new one takes over. Guests get nothing.
- Tools: get_view (project, tab, document, selection with names,
  camera, play state, open dialog) and screenshot. The resource
  feuerwerk://view can be subscribed. Claude Code does not act on
  that reliably, so a changed view is also noted on the next answer.
- A badge next to the account menu shows the connected agents. It
  counts only agents with an open stream or a request in the last
  two minutes.
- CI starts the relay in front of php -S (tools/ci/serve.sh), and
  e2e 71 runs the whole path in the browser.

Found on the live test: the badge showed four agents because old
sessions of revoked tokens were still counted.

Tests:
- Gate on atx: 316 files, 4888 tests
- relay protocol test with fake API and fake tabs: 23/23
- get_view, tools, socketUrl: 16/16
- PHP agents 29, rights 103 checks
- e2e 71 on atx 10/10, against the live site 10/10, no CSP violation
- real Claude Code against the live site: get_view answered
- ZAP against /mcp: nothing at High or Medium
- every new check fails when the guard it covers is taken out (6)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.gitea/workflows/ci.yml

@@ -35,8 +35,9 @@ jobs:
         env:
           GM_TEST_WORKERS: 2
 
-      # The API's own rules (#180, #179, #231, #266, #427). Not part of check.sh: the host the editor is
-      # built on has no PHP, the image does. rights.test.php runs the API itself under `php -S`.
+      # The API's own rules (#180, #179, #231, #266, #427, #429). Not part of check.sh: the host the
+      # editor is built on has no PHP, the image does. rights.test.php runs the API itself under
+      # `php -S`.
       - name: PHP tests
         run: |
           php tests/php/accounts.test.php
@@ -46,6 +47,7 @@ jobs:
           php tests/php/videos.test.php
           php tests/php/limits.test.php
           php tests/php/demos.test.php
+          php tests/php/agents.test.php
           php tests/php/rights.test.php
 
   suite: