feat(FN-3011): merge fusion/fn-3011

Commits merged:
- test(FN-3011): complete Step 2 — harden light-theme source assertions
- feat(FN-3011): complete Step 1 — restore global token scope
- fix(FN-3011): complete Step 3 — satisfy lint/test/typecheck/build gates
- test(FN-3011): complete Step 2 — harden light-theme source assertions
- feat(FN-3011): complete Step 1 — restore default light token ownership

Files changed:
.../app/__tests__/status-colors-theme.test.ts      | 100 +++++--
 .../app/components/CustomModelDropdown.css         |   6 -
 .../__tests__/ModelOnboardingModal.test.tsx        |   4 +-
 packages/dashboard/app/styles.css                  | 299 +++++++++++----------
 packages/dashboard/app/test/cssFixture.ts          |  11 +-
 5 files changed, 242 insertions(+), 178 deletions(-)

Fusion-Task-Id: FN-3011

packages/dashboard/app/components/CustomModelDropdown.css

@@ -347,12 +347,6 @@ html .column.drag-over * {
   --surface: #f6f8fa;
   --card: #ffffff;
   --card-hover: #f3f4f6;
-  /* Light mode keeps the same semantic role with slightly softer contrast. */
-  --surface-hover: color-mix(in srgb, var(--surface) 92%, var(--text) 8%);
-  --surface-subtle: color-mix(in srgb, var(--surface) 98%, var(--text) 2%);
-  --surface-muted: color-mix(in srgb, var(--surface) 97%, var(--text) 3%);
-  --surface-emphasis: color-mix(in srgb, var(--surface) 95%, var(--text) 5%);
-  --surface-hover-strong: color-mix(in srgb, var(--surface) 94%, var(--text) 6%);
   --bg-secondary: #f6f8fa;
   --bg-tertiary: #eaeef2;
   --border: #d0d7de;