Add deterministic staffing gather tool

[olegbrok]

Summary

• add a standalone Python 3.11 staffing gather that consumes authoritative btsprobe.scan classifications, joins bts_board.json, and optionally joins exact-key Desk counts
• derive free windows only inside 08:00–18:00 LA while preserving appt / build / queue / ooo blocks and keeping group-calendar blocks separate
• fail closed with source/member _err details for unreadable, inaccessible, malformed, or ambiguous inputs, including the two-Daniels exact-key boundary
• add the delivered redacted fixtures and contract regressions for range semantics, access failures, OOO, the 17→18 boundary, Desk absence versus zero, Bearer auth, and source failures

Internal task #543. This PR intentionally does not auto-close GitHub issue #543, which is unrelated.

Validation

• uv run pytest -q tests/test_staffing_gather.py — 19 passed
• uv run ruff check . — passed
• uv run python -m py_compile scripts/staffing_gather.py tests/test_staffing_gather.py — passed on Python 3.11.15
• fixture schema/semantic comparison and executable CLI smoke test — passed
• git diff --cached --check — passed before commit

The repository-wide suite reaches the known unrelated #1024 hermeticity defect: tests/test_api.py::TestAPI::test_manual_dream_uses_full_persisted_conversation_history escapes its SDK mock through this box's tmux transport and launches a real bundled Claude process. A fail-fast run reported 1 failed, 619 passed, 2 skipped. This PR does not touch that path.

The live scheduler/Pi integration cannot be exercised from this worktree. Per the task split, Geordi will integrate and verify the output against a live scheduler screenshot before it becomes an input to staffing decisions.

🤖 Opened by Kuzya

[olegbrok]

Orchestrator pass (gate is Murzik's): every contract ruling from the spec has a named test — 8-18 bounds with the 17-start→18-end boundary pinned, from-inclusive/to-exclusive proven at the range iterator, four scan buckets verbatim with free strictly derived, group as a separate stream (plus out-of-range-day detection beyond spec), two-Daniels exact-key isolation, Desk absent-vs-zero AND present-zero-vs-absent distinctness, per-member access fail-closed, null-source ≠ absent. The two beyond-spec fail-closed tests (non-whole-hour block, unknown scan type → error instead of manufactured free time) are exactly the right paranoia for a staffing matrix. Stdlib-only confirmed, no daemon imports. #1024 full-suite exception disclosure noted and accepted — known-failing test, unrelated. Ready for the gate from my side.

🤖 Barsik