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>

src/editor/agent/tools.json

@@ -0,0 +1,27 @@
+[
+  {
+    "name": "get_view",
+    "title": "What the user sees",
+    "description": "What the user is looking at in the editor right now: the project, the open tab and document, the selection (asset, scene objects, graph nodes, keys, ...), the camera of the view showing, whether the game is playing or paused, and an open dialog. Call it first, and again whenever you were told the view changed.",
+    "inputSchema": { "type": "object", "properties": {}, "additionalProperties": false },
+    "annotations": { "readOnlyHint": true, "openWorldHint": false }
+  },
+  {
+    "name": "screenshot",
+    "title": "Screenshot of the editor",
+    "description": "The whole editor as the user sees it, as a PNG: toolbar, panels, the open tab, menus and dialogs included. Scaled down to maxWidth pixels (default 1280) if it is wider.",
+    "inputSchema": {
+      "type": "object",
+      "properties": {
+        "maxWidth": {
+          "type": "integer",
+          "minimum": 320,
+          "maximum": 3840,
+          "description": "Widest the picture may be, in pixels."
+        }
+      },
+      "additionalProperties": false
+    },
+    "annotations": { "readOnlyHint": true, "openWorldHint": false }
+  }
+]