refactor(theme): retire the --color-* shim — the sweep it promised, run

#2533. theme.css claimed "removing this block is a rename sweep across the
components, tracked separately" — written in 67a529a, never filed, which made
the comment itself an instance of the survey's presence-without-reference
pattern. This is that sweep.

73 alias declarations deleted; 69 files rewritten; every --color-*-style name
now references its --fs-* token directly. Mechanical by construction: the map
IS the alias block, applied longest-name-first with a boundary guard so
--color-text never matched inside --color-text-muted. Zero survivors outside
theme.css, verified by grep rather than assumed.

One deliberate survivor: --color-shadow stays DECLARED, because it was never
an alias — it is a literal value the design system has no token for. Marked
in place as a recorded gap: promote it to an --fs-* token when a second app
needs it, don't copy the line.

Nothing is lost mode-wise: the aliases' resolve-at-use-time trick (which
absorbed 48 dark-mode overrides) lives one layer down in the --fs-* tokens'
own derivations, which is why the sweep is a pure rename. Both CSS checkers
green.

Why now rather than never: check_snippets_against_design_system reports every
--color-* reference as "unknown — renders as NOTHING", and nine recipe
snippets recorded from components.css carried the deprecated names, making
them prior art pointing the wrong way. With the sweep in, the checker's
report over re-recorded snippets should be EMPTY — the acceptance test that
proves the checker was right all along (#2517's correction).

Refs #2533

frontend/src/assets/theme.css

@@ -188,126 +188,21 @@
  */
 
 /* ==========================================================================
-   COMPATIBILITY ALIASES — the app's historical names, pointing at the system.
-
-   These exist so ~55 components keep working while they migrate to --fs-*
-   one at a time. Every one is a plain var() reference, which is what lets this
-   block be declared ONCE: when [data-theme="light"] moves --fs-surface-page,
-   --color-bg follows, because the alias resolves at use time.
-
-   That is why this file lost 48 of its 60 dark-mode overrides — they were all
-   restating relationships the aliases now express directly.
-
-   Removing this block is a rename sweep across the components, tracked
-   separately. Nothing new should reference a --color-* name.
+   The compatibility-alias block that lived here is GONE (#2533). It let ~55
+   components keep their historical --color-* names while theme.css was
+   repointed at the design system; the rename sweep it promised ran on
+   2026-08-08 and every component now references --fs-* directly. Do not
+   reintroduce app-local alias names — the design system's tokens are the
+   vocabulary, and check_snippets_against_design_system can only see through
+   names the system actually declares.
    ========================================================================== */
 
 :root {
-  /* surfaces */
-  --color-bg: var(--fs-surface-page);
-  --color-bg-secondary: var(--fs-surface-raised);
-  --color-bg-card: var(--fs-surface-raised);
-  --color-surface: var(--fs-surface-hover);
-  --color-code-bg: var(--fs-surface-code);
-  --color-code-inline-bg: var(--fs-surface-code-inline);
-  --color-table-stripe: var(--fs-table-stripe);
-  --color-overlay: var(--fs-overlay);
-
-  /* text */
-  --color-text: var(--fs-text-primary);
-  --color-text-secondary: var(--fs-text-secondary);
-  --color-text-muted: var(--fs-text-tertiary);
-
-  /* lines */
-  --color-border: var(--fs-border-color);
-  --color-input-border: var(--fs-border-color);
-  --focus-ring: var(--fs-focus-ring);
-
-  /* brand */
-  --color-primary: var(--fs-accent);
-  --color-primary-solid: var(--fs-accent);
-  --color-primary-deep: var(--fs-accent-deep);
-  --color-primary-faint: var(--fs-accent-faint);
-  --color-primary-tint: var(--fs-accent-soft);
-  --color-primary-wash: var(--fs-accent-wash);
-  --color-tag-bg: var(--fs-accent-soft);
-  --color-tag-text: var(--fs-accent);
-  --color-wikilink: var(--fs-wikilink);
-  --color-wikilink-bg: var(--fs-accent-soft);
-  --gradient-cta: var(--fs-gradient-cta);
-  --glow-cta: var(--fs-glow-cta);
-  --glow-cta-hover: var(--fs-glow-cta-hover);
-
-  /* actions */
-  --color-action-primary: var(--fs-action-primary);
-  --color-action-primary-hover: var(--fs-action-primary-hover);
-  --color-action-secondary: var(--fs-action-secondary);
-  --color-action-secondary-hover: var(--fs-action-secondary-hover);
-  --color-action-destructive: var(--fs-action-destructive);
-  --color-action-destructive-hover: var(--fs-action-destructive-hover);
-
-  /* semantic */
-  --color-success: var(--fs-success);
-  --color-warning: var(--fs-warning);
-  --color-danger: var(--fs-error);
-  --color-overdue: var(--fs-overdue);
-  --color-toast-success: var(--fs-success);
-  --color-toast-error: var(--fs-error);
+  /* A VALUE, not an alias — the one survivor of the alias block. The design
+     system has no shadow-colour token yet, so this is a recorded gap: when a
+     second app needs it, promote it to an --fs-* token in the system and
+     regenerate, rather than copying this line. */
   --color-shadow: rgba(0, 0, 0, 0.4);
-
-  /* task status + priority */
-  --color-status-todo: var(--fs-status-todo);
-  --color-status-todo-bg: var(--fs-status-todo-bg);
-  --color-status-in-progress: var(--fs-status-in-progress);
-  --color-status-in-progress-bg: var(--fs-status-in-progress-bg);
-  --color-status-done: var(--fs-status-done);
-  --color-status-done-bg: var(--fs-status-done-bg);
-  --color-priority-low: var(--fs-priority-low);
-  --color-priority-low-bg: var(--fs-priority-low-bg);
-  --color-priority-medium: var(--fs-priority-medium);
-  --color-priority-medium-bg: var(--fs-priority-medium-bg);
-  --color-priority-high: var(--fs-priority-high);
-  --color-priority-high-bg: var(--fs-priority-high-bg);
-
-  /* geometry */
-  --radius-sm: var(--fs-radius-sm);
-  --radius-md: var(--fs-radius-lg);   /* NB: the app's "md" is the system's LARGE */
-  --radius-lg: var(--fs-radius-xl);   /* and the app's "lg" is the system's XL */
-  --page-max-width: var(--fs-layout-page-max);
-  --page-padding-x: var(--fs-layout-page-pad);
-  --sidebar-width: var(--fs-layout-sidebar);
-  --header-height: var(--fs-layout-header);
-
-  /* ------------------------------------------------------------------
-     Names components reference that were NEVER declared anywhere.
-
-     Each of these was reached for with a hardcoded fallback, so the page
-     rendered — but the fallback was what rendered, always, and several were
-     off-palette: --color-primary-bg fell back to an indigo, --color-destructive
-     to a brick that is not the oxblood, --color-status-cancelled to a grey from
-     no palette in this system.
-
-     Wiring them to real tokens is the whole point of the exercise. Expect small
-     visual shifts exactly where a fallback had drifted; that shift IS the fix.
-     ------------------------------------------------------------------ */
-  --color-accent: var(--fs-accent);
-  /* Foreground ON the accent, so it follows the accent's mode-independence,
-     not the page text's. Pointing this at --fs-text-primary made it invert to
-     obsidian on light — over a mid-tone accent, well under the AA floor. */
-  --color-accent-fg: var(--fs-text-on-action);
-  --color-hover: var(--fs-surface-hover);
-  --color-bg-hover: var(--fs-surface-hover);
-  --color-bg-tertiary: var(--fs-surface-hover);
-  --color-surface-2: var(--fs-surface-hover);
-  --color-surface-alt: var(--fs-surface-hover);
-  --color-surface-raised: var(--fs-surface-raised);
-  --color-input-bg: var(--fs-surface-page);
-  --color-muted: var(--fs-text-tertiary);
-  --color-destructive: var(--fs-destructive);
-  --color-primary-bg: var(--fs-accent-soft);
-  --color-status-cancelled: var(--fs-status-cancelled);
-  --font-display: var(--fs-font-display);
-  --font-mono: var(--fs-font-mono);
 }
 
 /* ==========================================================================