PR #1310 — Fleet Parity: Agy Stitch MCP Integration, Diagnostics, and Prompt Guidance

The Broader Goal at the End of the Previous PR

PR #1309 closed issue #347, completing the entire original fleet parity cluster (#332, #338, #340, #342, #347, #348, #419, #461). Next on the roadmap was issue #573: investigating and resolving why Agy (Google Antigravity CLI) was reported unable to invoke Stitch MCP tools in headless dispatches.

What Was Missing & The Real Root Cause

1. Configuration Gap: Stitch had been installed via the Gemini CLI extension installer (gemini extensions install https://github.com/gemini-cli-extensions/stitch), which placed extension metadata under ~/.gemini/extensions/Stitch/. But synlynk dispatch agy invokes the Antigravity CLI (agy), which does not read ~/.gemini/extensions/. Antigravity loads MCP servers exclusively from ~/.gemini/config/mcp_config.json, which was empty.
2. Tool Invocation Paradigm Mismatch: Prompts assumed the Claude Code convention of flat, prefixed tool names (mcp__stitch__*). In Antigravity CLI, MCP tools are invoked through the built-in meta-tool call_mcp_tool(server="stitch", tool="<tool_name>", arguments={...}).
3. Live Verification: Once stitch was added to ~/.gemini/config/mcp_config.json (npx -y stitch-mcp@1.0.0 with project gen-lang-client-0187568210), live headless dispatch verified that call_mcp_tool executed without permission prompts, successfully returning live Stitch projects.

What Shipped

1. Capability Baseline Update: Added stitch.googleapis.com:443 to optional network endpoints for Agy in synlynk/_constants.py.
2. TC-8 Doctor Preflight: Added _run_tc8() in synlynk/doctor.py asserting that ~/.gemini/config/mcp_config.json has an active, enabled stitch server configuration.
3. Doctor Auto-Remediation: Added _build_agy_stitch_fix_plan() to synlynk doctor --fix agy for one-command remediation.
4. Dispatch Preflight & Prompt Adaptation:
   • Enforced --requires stitch / --requires mcp checks in synlynk/dispatch.py:_preflight_dispatch().
   • Injected the ## Stitch MCP Tool Usage Note reminding Agy to invoke call_mcp_tool whenever Stitch is referenced.
5. Tests: Added comprehensive unit tests in tests/test_synlynk.py and tests/test_dispatch.py. All 504 tests pass.