feat(hyprland): themed backdrop — misc:background_color from the palette (item 28c)

The compositor backdrop behind a missing or still-loading wallpaper
was hard black; on light themes that flash reads as a glitch (caught
by the 1080p capture harness on summer-day). Now the theme's base
color, so every wallpaper-less moment stays in-palette.

Also from the summer-day capture review: the authored whole-swap menu
+ island bar survive the 28b retunes as one coherent identity (the
slate menu deliberately mirrors the bar strip — an earlier "polarity"
concern retracted); nit filed for the undimmed placeholder in the two
summer rasi. Punch list updated in item 28.

Verified: V0; V1 — template-home rebuilt, hyprland.conf renders
background_color=rgb(1a1b26). Visual confirmation rides the next
capture run.

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

agent/BACKLOG.md

@@ -82,9 +82,20 @@ review:
   - **Semantic dim:** bar dim states are `alpha(@text, 0.5)` tints;
     the palette's `muted` role is now floor-guaranteed (28b) — one
     semantic source, use `@muted`.
+  - ✓ **compositor backdrop** (shipped iteration #35): Hyprland
+    `misc:background_color` now the theme's base — no more black flash
+    behind a missing/slow wallpaper (glaring on light themes in the
+    summer-day capture).
+  - summer-day whole-swap capture reviewed (iteration #35): the
+    authored slate menu + island-pill bar survive the 28b retunes and
+    read as one coherent identity — keep. One nit: its rasi doesn't
+    dim the entry placeholder, so "Menu Type to search…" reads as one
+    run-on phrase (generated theme dims it; mirror that in the two
+    summer rasi).
   - Harness gap: wallpaper needs `~/.nomarchy` seeded in the guest
     (theme-sync reads runtime state there) — add before vibe-review
-    captures; whole-swap captures (summer-day/night) still pending;
+    captures; latte + an identity theme (lumon/retro-82) captures
+    still pending;
 (d) the whole-swap themes brought to the same bar (module parity
 verified textually 2026-07-05: whole-swaps carry every functional
 module; omitting cpu/memory is identity). Visual work is

agent/JOURNAL.md

@@ -17,6 +17,26 @@ Template:
 
 ---
 
+## 2026-07-05 — summer-day capture review + themed backdrop (iteration #35, item 28c)
+- **Task:** item 28 slice (c) — whole-swap capture review + the first
+  cheap polish fix.
+- **Did:** captured summer-day at 1080p (harness, VM): the authored
+  slate menu + island-pill bar hold up with the 28b retunes —
+  initially misread as polarity soup, but the rasi whole-swap
+  deliberately mirrors the bar's slate strip: identity, keep (nit
+  filed: undimmed entry placeholder). The surviving cross-theme fix:
+  Hyprland `misc:background_color` = theme base (was compositor
+  black — a glitch-looking flash behind missing/slow wallpaper,
+  glaring on light themes). Punch list updated.
+- **Verified:** V0; V1 — template-home rebuilt, rendered hyprland.conf
+  carries `background_color=rgb(1a1b26)` (theme base). Backdrop
+  visible confirmation rides the next capture run / V3.
+- **Pending:** captures for latte + one identity theme; polish items
+  queued: bar group margins, @muted adoption, rofi hint column, icon
+  weight `[human]`.
+- **Next suggestion:** bar polish slice (group margins + @muted) —
+  code-level, verifiable by build + re-capture.
+
 ## 2026-07-05 — 1080p capture harness + first slice-c review (iteration #34, item 28c)
 - **Task:** item 28 slice (c) prep — full-res captures for the
   per-surface polish pass.

modules/home/hyprland.nix

@@ -377,6 +377,11 @@ in
         disable_hyprland_logo = lib.mkDefault true;
         disable_splash_rendering = lib.mkDefault true;
         force_default_wallpaper = lib.mkDefault 0;
+        # The backdrop when no wallpaper is painted (awww still starting,
+        # a slow first paint, or a wallpaper-less setup): the theme's base
+        # instead of compositor black — on light themes the black flash
+        # reads as a glitch (item 28c, seen in the capture harness).
+        background_color = rgb c.base;
       };
 
       # Rendered from ./keybinds.nix (the cheatsheet reads the same list),