fix(cli): bound Gateway RPC response waits

[ptterjgf]

Scope

Scope boundary: Bound CLI Gateway RPC response waits, clean up pending futures on timeout/cancellation/close, and release the subscription lock after an unsubscribe frame is sent but before its response is awaited.

Non-goals: Retrying ambiguous RPCs such as sessions.send, changing Gateway server behavior, or adding a stream-idle timeout.

Branch

Base branch: main

Target exception: N/A

Issue

Linked issue: Fixes #1507

If None, reason: N/A

Release Note

Release note: CLI chat requests now time out cleanly when a connected Gateway stops answering, and a lost unsubscribe response no longer blocks later turns.

Tests

Ruff: uv run ruff check src tests — passed.

Pytest:

• uv run pytest tests/test_cli/test_gateway_client_keepalive.py -q — 35 passed.
• Gateway client / CLI RPC / chat runtime regression set — 91 passed.
• PYTHONUTF8=1 uv run pytest tests/test_ci/test_migration_v011.py -q — 4 passed.
• Full-suite diagnostics reached 1,487 passed / 66 skipped before the Windows default GBK locale made yoyo decode a UTF-8 migration incorrectly. With UTF-8 mode, tests/test_ci reached 352 passed / 3 skipped before the host-only requirement for native Git Bash stopped test_pr_change_selection_uses_merge_base_and_ignores_base_only_changes. Neither blocker touches this change.

Build:

• Web UI typecheck, architecture guards, Vite build, and 397-file artifact verification passed. The automation host blocked the final recursive staging write; after staging the already verified bytes, node scripts/stage-dist.mjs --check passed.
• uv build --wheel — passed (opensquilla-0.5.4-py3-none-any.whl).

Regression tests: added

Notes: Covers silent response timeout, cancellation cleanup, clean-close wakeup, late responses, successful follow-up RPCs, RPC error details, and unsubscribe/subscribe ordering without lock starvation.

The default test path remains offline, deterministic, credential-free, and safe for forks.

Maintainer Live Check

Maintainer live check: no

Surface: gateway

Maintainer-only note: No credentialed check is needed; the regression uses an offline response-silent WebSocket double.

Safety

No secrets, local-only artifacts, private prompts/transcripts, channel identifiers, AI session artifacts, non-public fixtures, or tests/_private/ contents are included.

Third-Party Origin

Third-party origin: none

Details if non-none: N/A

Documentation Changes

• Links point to existing repository files or stable external pages.
• Code fences and Markdown tables render correctly on GitHub.
• Examples avoid real secrets, local private paths, and private transcripts.