Handle empty Antigravity print results

[SpadesZ]

Summary

• Treat agy --print stdout as diagnostic and keep completion tied to report MCP/result marker.
• Ignore legacy unsafe ANTIGRAVITY_AGY_MODEL=Gemini 3.5 Flash (Medium) and remove that default from install templates.
• Add Antigravity conversation SQLite fallback: when stdout is empty but a non-user response step contains DEV_TRIANGLE_RESULT_READY, Dev Triangle recovers the result into the mailbox and marks the handoff complete.
• Document the physical recovery path and no-hardcoded-model rule so future installs do not reintroduce this failure.

Root Cause

Antigravity CLI can authenticate, stream model/tool activity, and still return exit 0 with empty stdout. On this Windows machine the model response was present in %USERPROFILE%\.gemini\antigravity-cli\conversations\*.db, while stdout stayed empty. The correct durable completion signal is the report MCP/result marker, with SQLite DB recovery as a local fallback.

Verification

• python -m py_compile server.py antigravity_report_server.py tests/protocol_smoke.py tests/report_server_smoke.py
• python tests/protocol_smoke.py
• python tests/report_server_smoke.py
• git diff --check
• scripts/smoke.ps1
• Real local smoke: patched run_antigravity_print_smoke(...) passed via antigravity_conversation_db fallback while raw stdout was empty.
• Real blocked handoff antigravity-20260626052726-f572619f reran successfully and submitted through dev-triangle-report; ledger/result status is COMPLETED, recommendation MERGE.

[SpadesZ]

Update: added Windows agy recovery hardening in a6b67f2. The runner now starts agy from USERPROFILE, passes target repo via --add-dir, records --log-file, recovers completed results from Antigravity transcript JSONL, keeps existing conversation DB fallback, and can mark timeout cases COMPLETED when a ready fallback result exists. Validation: py -3.12 py_compile, tests/protocol_smoke.py, tests/report_server_smoke.py, scripts/smoke.ps1 all pass. Real agy health smoke passed via fallback with agy available, stdout empty, timedOut true, fallbackFound true.