refactor(theme): remove 184 var() fallbacks — every one was unreachable

#2277 counted ~150 "raw colour literals bypassing the tokens". Measuring them
told a different story: 184 sat in `var(--token, #fallback)` position, and a
check against theme.css shows every one of those tokens IS declared. So the
fallbacks could not render. Not drift — vestigial.

They were also not this palette. The most common were Tailwind and Flat-UI
defaults — #6366f1 indigo, #22c55e green, #f59e0b amber, #3b82f6 blue,
#e74c3c and #27ae60 — a second, unsanctioned colour scheme sitting in the
codebase looking like the app's colours to anyone reading it.

Removing them is not tidying. #2319's lesson is that a fallback is WORSE than a
missing token: a missing token renders as nothing and someone eventually
notices, while a fallback renders something plausible forever. These 184 were
one token rename away from silently repainting the app in Tailwind. The design
token check would catch the rename — but the fallback is precisely the thing
that would make it invisible if the check were ever bypassed.

Literal count 152 -> 45, which matters beyond the number: a report that is
mostly unreachable noise is one people stop reading, and then it stops working
while still passing. What remains should be genuinely worth looking at.

Done with a paren-aware transform, not a regex — `var(--x, rgba(0,0,0,.5))`
nests parens and `[^)]+` would cut at the first one and leave `))` behind.
Verified after: every changed line is a fallback strip and nothing else, and
every var() reference still resolves.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UaYUaouG9jjhATyuxCKrQs

frontend/src/views/TaskEditorView.vue

@@ -874,7 +874,7 @@ useEditorGuards(dirty, save);
   padding: 0 0.2rem;
   flex-shrink: 0;
 }
-.btn-clear-parent:hover { color: var(--color-danger, #e74c3c); }
+.btn-clear-parent:hover { color: var(--color-danger); }
 .parent-dropdown {
   position: absolute;
   top: calc(100% + 4px);
@@ -1037,13 +1037,13 @@ useEditorGuards(dirty, save);
   margin: 0.5rem 0 0.25rem;
 }
 .task-goal-label {
-  font-family: var(--font-display, "Fraunces", serif);
+  font-family: var(--font-display);
   font-style: italic;
   font-size: 0.78rem;
   font-weight: 500;
   letter-spacing: 0.04em;
   text-transform: uppercase;
-  color: var(--color-text-muted, rgba(255, 255, 255, 0.5));
+  color: var(--color-text-muted);
 }
 .task-goal-input {
   width: 100%;
@@ -1053,14 +1053,14 @@ useEditorGuards(dirty, save);
   font: inherit;
   font-size: 0.95rem;
   line-height: 1.4;
-  color: var(--color-text, inherit);
-  background: var(--color-input-bg, rgba(255, 255, 255, 0.03));
-  border: 1px solid var(--color-border, rgba(255, 255, 255, 0.08));
-  border-radius: var(--radius-md, 8px);
+  color: var(--color-text);
+  background: var(--color-input-bg);
+  border: 1px solid var(--color-border);
+  border-radius: var(--radius-md);
 }
 .task-goal-input:focus {
   outline: none;
-  border-color: var(--color-primary, #6366f1);
+  border-color: var(--color-primary);
 }
 
 /* ── Auto-summary banner + re-consolidate button ─────────────────────────── */
@@ -1072,13 +1072,13 @@ useEditorGuards(dirty, save);
   margin-bottom: 0.5rem;
   font-size: 0.82rem;
   font-style: italic;
-  color: var(--color-text-muted, rgba(255, 255, 255, 0.6));
+  color: var(--color-text-muted);
   background: rgba(99, 102, 241, 0.06);
-  border-left: 2px solid var(--color-primary, #6366f1);
-  border-radius: var(--radius-sm, 4px);
+  border-left: 2px solid var(--color-primary);
+  border-radius: var(--radius-sm);
 }
 .auto-summary-banner-editor .auto-summary-icon {
-  color: var(--color-primary, #6366f1);
+  color: var(--color-primary);
   font-style: normal;
 }
 </style>