fix(swaync): palette-safe pairings — text was invisible on summer-day (item 25)

Palette roles aren't uniform: summer-day and flexoki-light use subtext
as text-ON-surface (== base) and surface as a dark chip (== text), so
swaync's @subtext-on-@base body text and @surface/@text buttons were
self-colored (caught on the Latitude).

- body/summary: @text on @base — the one text pairing that passes in
  every palette (survey: worst WCAG ratio 5.18 across all 21 themes;
  subtext/base bottomed at 1.00 twice, muted/base at 1.27).
- hover rows + widget-title buttons: alpha(@text, 0.1) tints —
  contrast by construction; subtext/surface defines dropped.
- NEW checks.theme-contrast (tools/check-theme-contrast.py): asserts
  the hex-on-hex text pairings across themes/*.json, cheap (no VM).

The audit also found the generated waybar/rofi CSS shares the bug
class, live on flexoki-light (no whole-swap) → BACKLOG item 27.

Verified: V0; V1 (checks.theme-contrast builds green, 21 themes;
rendered services.swaync.style has zero @subtext/@surface). Honesty:
NOT visually verified — V3 queued (notify-send on summer-day).

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

docs/ROADMAP.md

@@ -849,6 +849,17 @@ how to override it. Items marked ✓ are shipped.
   your theme / essentials" flow (ties into the branding work).
 
 ## Known issues & follow-ups
+- ✓ **swaync text invisible on summer-day** (Latitude QA, 2026-07-04):
+  the themed CSS paired @subtext on @base, but palette roles are not
+  uniform across themes — summer-day/flexoki-light use subtext as
+  text-*on*-surface (== base) and surface as a dark chip (== text), so
+  body text and widget buttons self-colored. Fix: swaync uses only
+  pairings safe in every palette — @text on @base for text (survey:
+  worst ratio 5.18 across 21 themes) and alpha(@text, 0.1) tints for
+  chips/hovers — guarded permanently by `checks.theme-contrast`
+  (tools/check-theme-contrast.py, WCAG ratios over themes/*.json).
+  The same audit found generated waybar/rofi CSS shares the bug class,
+  exposed on flexoki-light (BACKLOG item 27).
 - ✓ **Waybar crash on theme switch left the session bar-less** (Latitude
   hardware QA, 2026-07-04): exec-once has no supervisor, so any crash
   orphaned the session until relogin — and the switch path itself was