fix(cli): recall general checkpoints at session start

[Shunkleburger]

Summary

• recall general session checkpoints alongside harness session notes
• include active as well as open decisions in the SessionStart brief
• preserve repository-scoped coding-session isolation

Verification

• uv run pytest tests/cli/test_hook_command.py tests/cli/test_coding_session_context.py -q (136 passed)
• focused Ruff format and lint checks passed
• focused ty check passed
• live Codex SessionStart probe returned the active decision and four recent TTRPG-Wiki checkpoints

Note

just is unavailable in this checkout. Its documented full typecheck equivalent (uv run ty check src tests test-int) is blocked by missing optional pymilvus imports unrelated to this PR.

[CLAassistant]

All committers have signed the CLA.