fix(gateway): stop typing before post-delivery callbacks

[konsisumer]

What does this PR do?

Fixes a gateway cleanup ordering bug where a hung post-delivery callback could prevent _process_message_background() from stopping the platform typing indicator. The adapter now stops typing before running deferred callback work and bounds awaited callbacks to 30 seconds so callback I/O cannot keep the cleanup path stuck indefinitely.

Related Issue

Refs #24971

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature (non-breaking change that adds functionality)
• 🔒 Security fix
• 📝 Documentation update
• ✅ Tests (adding or improving test coverage)
• ♻️ Refactor (no behavior change)
• 🎯 New skill (bundled or hub)

Changes Made

• gateway/platforms/base.py: stop the _keep_typing task and explicitly clear platform typing before post-delivery callbacks run; wrap awaited post-delivery callbacks in a 30-second timeout.
• tests/gateway/test_run_progress_topics.py: add regression coverage proving a hung post-delivery callback does not keep typing alive or block message processing indefinitely.

How to Test

1. $VIRTUAL_ENV/bin/python -m pytest tests/gateway/test_run_progress_topics.py::test_base_processing_releases_post_delivery_callback_after_main_send tests/gateway/test_run_progress_topics.py::test_base_processing_stops_typing_before_hung_post_delivery_callback -q — passed.
2. $VIRTUAL_ENV/bin/python -m pytest tests/ -q -x --timeout=60 — failed after 5:25 in tests/acp/test_approval_isolation.py::TestAcpExecAskGate::test_interactive_env_var_routes_to_callback, outside the gateway files touched by this PR.
3. $VIRTUAL_ENV/bin/python -m ruff check gateway/platforms/base.py tests/gateway/test_run_progress_topics.py — passed.
4. $VIRTUAL_ENV/bin/python scripts/check-windows-footguns.py gateway/platforms/base.py tests/gateway/test_run_progress_topics.py — passed.
5. git diff --check — passed.
6. $VIRTUAL_ENV/bin/python -m ruff format --check gateway/platforms/base.py tests/gateway/test_run_progress_topics.py — failed because these existing files would be reformatted wholesale; this PR leaves unrelated formatting untouched.

Checklist

Code

• I've read the Contributing Guide
• My commit messages follow Conventional Commits (fix(scope):, feat(scope):, etc.)
• I searched for existing PRs to make sure this isn't a duplicate
• My PR contains only changes related to this fix/feature (no unrelated commits)
• I've run pytest tests/ -q and all tests pass
• I've added tests for my changes (required for bug fixes, strongly encouraged for features)
• I've tested on my platform: macOS 15.6 arm64 (Darwin 24.6.0)

Documentation & Housekeeping

• I've updated relevant documentation (README, docs/, docstrings) — or N/A
• I've updated cli-config.yaml.example if I added/changed config keys — or N/A
• I've updated CONTRIBUTING.md or AGENTS.md if I changed architecture or workflows — or N/A
• I've considered cross-platform impact (Windows, macOS) per the compatibility guide — or N/A
• I've updated tool descriptions/schemas if I changed tool behavior — or N/A

For New Skills

N/A

Screenshots / Logs

N/A