fix(display): stop the run loop spinning when no mode has anything to show (#649)

* fix(display): stop the run loop spinning when no mode has anything to show

A mode whose display() reports nothing rotates to the next at once, with no
dwell. With every enabled mode empty (only a sports plugin in its
off-season, say) the loop went round with no sleep: on ledpi, 169% CPU and
~1,800 "No content" log lines every 10 seconds. After one full rotation of
empty passes it now pauses EMPTY_ROTATION_PAUSE (1s) per pass, servicing
plugin updates and returning early on on-demand or schedule changes; live
priority is still checked at the top of every pass, and the streak resets
as soon as any mode shows something.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* fix(display): restart the loop if the empty-rotation pause starts on-demand; per-rotation streak

- an on-demand request serviced during the pause returned early into the
  on-demand branch, which advanced past the mode just requested; the loop
  now restarts when the pause changed the mode, on-demand state or schedule
- the streak is reset when the rotation changes (on-demand start/stop, a
  plugin enabled or disabled), so a streak from one rotation can't make
  another pause before its own modes are tried
- docstring: live content is picked up within the pause, not "at once"

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

CHANGELOG.md

@@ -19,6 +19,8 @@ accepts both, but the store flags the old spelling as deprecated
 
 ## Unreleased
 
+- The display loop no longer spins at 100% CPU when no enabled mode has anything to show (for example, only a sports plugin enabled in its off-season). After one full rotation of empty modes it checks one mode per second until something shows; live content still takes over at once.
+
 - Contributor tooling and docs:
   - `mypy.ini` parses again. A multi-line `exclude` and trailing comments on values made mypy refuse the whole file, so none of its settings applied and the pre-commit hook failed with "Missing target". The mypy hook is now manual (`pre-commit run mypy --hook-stage manual`) while the ~500 existing type errors in `src/` are paid down.
   - `.gitignore` ignores everything in `config/` except the templates; `ytm_auth.json`, `saved_repositories.json`, `wifi_status.json` and `font_overrides.json` weren't ignored.