fix(mcp): stateless HTTP transport so client reconnects after redeploy

Stateful session manager strands Claude Code after a container redeploy:
it reconnects with a now-unknown Mcp-Session-Id, the server 404s, and the
client won't re-initialize on a 404 (claude-code #60949). Stateless makes
each request self-contained (bearer-auth only) so post-deploy reconnect
works without a manual /mcp retry.

src/fabledassistant/mcp/server.py

@@ -74,9 +74,18 @@ def build_mcp_server() -> FastMCP:
     behind a reverse proxy with bearer-token auth as the real security
     boundary.
     """
+    # stateless_http=True: don't hand the client a persistent Mcp-Session-Id.
+    # The stateful default strands Claude Code after a container redeploy —
+    # it reconnects with the now-unknown session id, the server returns 404,
+    # and the client won't re-initialize on a 404 (Claude Code issue #60949),
+    # so the connection stays dead until a manual /mcp retry. Stateless makes
+    # every request self-contained (bearer-auth only), so a post-deploy
+    # reconnect just works. Trade-off: no server-pushed list_changed stream,
+    # which we don't use — tools are re-fetched on reconnect anyway.
     mcp = FastMCP(
         "scribe",
         instructions=_INSTRUCTIONS.strip(),
+        stateless_http=True,
         transport_security=TransportSecuritySettings(
             enable_dns_rebinding_protection=False,
         ),