Make the darker tone true-black AMOLED

The darker tone sat at #090908 for --background while --chrome was already
pure black, which both inverted the elevation ramp (frame strips darker than
the content beside them) and missed the point of an AMOLED tone — only a
true #000000 pixel is actually off on OLED.

--background now collapses into --chrome at pure black, so the main window,
connection manager and editor all render black end to end: panes, bars,
sidebar, gutter and textarea. Elevation is kept where it earns its place —
dialogs, popovers and toasts stay #181817, hover and selection #272726 — and
--border/--input go from 12%/15% to 16%/18% white, since on pure black those
lines are the only thing left defining panes, bars and rows.

No plumbing needed: buildPreload already bakes data-dark-tone onto every
window pre-paint, and tone changes broadcast live to open windows.

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

docs/architecture.md

@@ -245,7 +245,10 @@ dark neutrals are a **warm gray family (hue 107)** anchored on `#1a1a19`
 and cool surfaces clash. Surface elevation ramp, both themes: `--chrome`
 (frame strips) sits *below* `--background` (content panes) < `--card`
 (popovers/dialogs) < `--accent` (hover). Dark ramp `#151514` → `#1a1a19` →
-`#20201f` → `#2e2e2d`; the "darker" tone drops `--chrome` to true black.
+`#20201f` → `#2e2e2d`. The "darker" tone is true-black AMOLED: `--chrome` AND
+`--background` are both `#000` (the frame/content step collapses on purpose),
+elevation survives only via `--card`/`--accent`, and `--border`/`--input` go to
+16%/18% white because those lines then carry the whole layout.
 `bg-chrome` is on the tab bar, status bar, transfer bar, the editor/manager
 header+footer strips and the manager's connection sidebar; panel-internal
 toolbars deliberately stay on `--background`. Accent tones: one

ui/src/index.html

@@ -15,10 +15,10 @@
     <style>
       html { background: oklch(1 0 0); }
       html[data-theme='dark'] { background: oklch(0.2178 0.002 107); }
-      html[data-theme='dark'][data-dark-tone='darker'] { background: oklch(0.141 0.002 107); }
+      html[data-theme='dark'][data-dark-tone='darker'] { background: oklch(0 0 0); }
       @media (prefers-color-scheme: dark) {
         html:not([data-theme='light']) { background: oklch(0.2178 0.002 107); }
-        html:not([data-theme='light'])[data-dark-tone='darker'] { background: oklch(0.141 0.002 107); }
+        html:not([data-theme='light'])[data-dark-tone='darker'] { background: oklch(0 0 0); }
       }
     </style>
   </head>

ui/src/styles.css

@@ -105,30 +105,35 @@
 }
 
 /* Dark tone "darker" (data-dark-tone set by SettingsService; absent = grey "dark").
-   Near-black AMOLED palette. Duplicated for forced-dark and system-dark like the
-   token blocks above — the extra attribute outranks them. */
+   True-black AMOLED palette: --chrome collapses into --background on purpose, so
+   the frame/content step of the default tone disappears and every large surface is
+   #000 (OLED pixels actually off). Elevation survives only through --card and
+   --accent; --border/--input are raised to 16%/18% because on pure black those
+   lines are the only thing defining panes, bars and rows. Duplicated for
+   forced-dark and system-dark like the token blocks above — the extra attribute
+   outranks them. */
 :root[data-theme='dark'][data-dark-tone='darker'] {
-  --background: oklch(0.141 0.002 107);
+  --background: oklch(0 0 0);
   --chrome: oklch(0 0 0);
   --card: oklch(0.21 0.002 107);
   --secondary: oklch(0.274 0.003 107);
   --muted: oklch(0.274 0.003 107);
   --muted-foreground: oklch(0.705 0.012 107);
   --accent: oklch(0.274 0.003 107);
-  --border: oklch(1 0 0 / 12%);
-  --input: oklch(1 0 0 / 15%);
+  --border: oklch(1 0 0 / 16%);
+  --input: oklch(1 0 0 / 18%);
 }
 @media (prefers-color-scheme: dark) {
   :root:not([data-theme='light'])[data-dark-tone='darker'] {
-    --background: oklch(0.141 0.002 107);
+    --background: oklch(0 0 0);
     --chrome: oklch(0 0 0);
     --card: oklch(0.21 0.002 107);
     --secondary: oklch(0.274 0.003 107);
     --muted: oklch(0.274 0.003 107);
     --muted-foreground: oklch(0.705 0.012 107);
     --accent: oklch(0.274 0.003 107);
-    --border: oklch(1 0 0 / 12%);
-    --input: oklch(1 0 0 / 15%);
+    --border: oklch(1 0 0 / 16%);
+    --input: oklch(1 0 0 / 18%);
   }
 }