Merge origin/main into main

Reconcile the staged-projection and Diagnostics feature work with the CI
quality-gate changes from origin/main. The origin side of every conflict was
lint-only, so the feature imports were kept and the ruff fixes re-applied:

- keep the branch's added imports (timefmt, activity_readout, projection
  ladder helpers) and drop the unused ones ruff reported
- restore `noqa: E402` on the post-bootstrap imports in fenris-monitor and
  keep the `noqa: F401` re-exports in the TUI that tests assert on
- make the TUI monitoring-glyph test clock-relative instead of pinned to a
  fixed date

tests/test_complete_observation_day_gate.py

@@ -15,7 +15,6 @@ Acceptance criteria:
 - Gate-3: Partial days don't satisfy the condition
 - Gate-4: CLI and TUI share the same gate via compute_projection()
 """
-import sqlite3
 from datetime import datetime, timedelta, timezone
 from pathlib import Path
 
@@ -26,8 +25,7 @@ sys.path.insert(0, str(Path(__file__).parent.parent / "src"))
 from fenris.store import init_store
 from fenris.monitoring_periods import ensure_period_open
 from fenris.projection import (
-    compute_projection, ConfidenceState, BaselineTier,
-    WARMING_COVERAGE_FLOOR,
+    compute_projection, ConfidenceState,
 )