feat(bar): idle-inhibit (caffeine) toggle — generated bar + summer-day parity (item 13 slice)

Summer-night's whole-swap bar had an idle_inhibitor the generated bar
lacked (reverse parity gap from the 2026-07-04 sweep). The generated
bar now carries it — 󰾪 click → 󰅶, warm tint while active, tooltips
saying what it holds — blocking hypridle's lock/display-off/suspend
for videos and presentations; state deliberately resets with the bar.
summer-day mirrors summer-night's module + CSS, and the keybinds
cheatsheet mentions the bar click (via keybinds.extra).

V1: rendered config has the module with correct glyphs, CSS rules
present, cheatsheet row renders. Inhibit behaviour needs a session →
V3 queued.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

agent/BACKLOG.md

@@ -27,11 +27,9 @@ next, in what order*.
 ## NEXT
 
 ### 13. Small niceties batch (one slice per iteration)
-Each is a small, self-contained polish item in the existing patterns:
-- **Idle-inhibit (caffeine) toggle:** Waybar `idle_inhibitor` module
-  (blocks hypridle lock/suspend during video/presentations) in the
-  GENERATED bar — summer-night already has one (reverse parity gap
-  found 2026-07-04); add to summer-day too + cheatsheet mention.
+Each is a small, self-contained polish item in the existing patterns
+(idle-inhibit/caffeine slice shipped 2026-07-04 — generated bar +
+summer-day parity + cheatsheet row):
 - **Low-battery notifications:** the bar colors at 25/10% but nothing
   *notifies*; gate on `power.laptop` (poweralertd, or a small upower
   watcher consistent with how the bar reads state).