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_activity_readout.py

@@ -3,7 +3,6 @@
 The readout is exercised against SQLite fixtures only; no Textual is involved.
 The local timezone is pinned through the TZ environment variable.
 """
-import sqlite3
 from datetime import datetime, timezone
 from pathlib import Path
 import sys