fix(gateway): refresh cached agent tools on /reload-mcp

When the gateway processes /reload-mcp, it reconnects MCP servers and
updates the global _servers registry, but cached AIAgent instances in
_agent_cache keep the tools list they were built with. The user had to
also run /new (discarding conversation history) before the agent could
see the new tools — even though /reload-mcp had succeeded.

This patch refreshes each cached agent's .tools and .valid_tool_names
in _execute_mcp_reload after discovery returns, so existing sessions
pick up new MCP tools on their next turn. The slash-confirm gate in
_handle_reload_mcp_command already obtains user consent for the
implied prompt-cache invalidation before this code runs.

Mirrors the equivalent behaviour the CLI already does in cli.py
_reload_mcp. Per-agent enabled_toolsets and disabled_toolsets are
preserved so an agent that was scoped to a subset of toolsets does
not silently gain disabled tools after the reload.

Original diagnosis + initial implementation in #23812 from @fujinice.
The auto-reload watcher half of that PR is intentionally dropped —
users want /reload-mcp to remain explicit.

Co-authored-by: fujinice <45688690+fujinice@users.noreply.github.com>

scripts/release.py

@@ -46,6 +46,7 @@ ACP_REGISTRY_MANIFEST = REPO_ROOT / "acp_registry" / "agent.json"
 # Auto-extracted from noreply emails + manual overrides
 AUTHOR_MAP = {
     "9592417+adam91holt@users.noreply.github.com": "adam91holt",
+    "45688690+fujinice@users.noreply.github.com": "fujinice",
     # teknium (multiple emails)
     "teknium1@gmail.com": "teknium1",
     "kenyon1977@gmail.com": "kenyonxu",