web-player: final sweep and guardrails

Add scripts/check-tokens.mjs (npm run lint:tokens, wired into lint) as
a guardrail: fails if src/**/*.svelte reintroduces arbitrary values
outside the B.4 allowlist, factory rounded-*, h-N w-N pairs (should
be size-N), quarter-step fractional spacing, or literal hex/rgba()
colors.

Cleans up the repo until the script reports 0 violations: ~40 h-N w-N
pairs -> size-N (mostly icons, via a one-off script), ~26 quarter-step
fractional spacings rounded to the nearest integer (delta <=1px, e.g.
py-2.75->py-3, gap-1.75->gap-2), stray factory radii (rounded-sm/lg,
bare rounded) migrated to the matching tokens, and two
tracking-[-0.02em] that matched the existing tracking-display token
exactly but had never been migrated. Removes the
stroke-thin/regular/bold recipes (added earlier, zero consumers) —
decision made, not blocking: strokeWidth={n} (13 values, across
almost every component) isn't migrated to CSS because there's no way
to verify without Docker that lucide-svelte honors stroke-width by
class instead of the prop, and a regression there would be silent
across the whole app; the script documents this gap explicitly
instead of pretending full coverage.

Orphan detector: 0 components with no importers. Removes
docs/design-system-refactor-plan.md (earlier plan, superseded by
frontend-refactor-plan.md). web-player/CLAUDE.md gains a "Styles"
section with the B.4 allowlist and the base components to reuse.
Recalculates the baseline table (A.4) and logs it: 61->47 components,
44->11 arbitrary values (the remaining 11 on the allowlist), 13->8
distinct radii, 0 lint:tokens violations.

Verified with npm run check (0 errors), npm run lint:tokens (0
violations) and npm run build. Smoke-tested /login with no console
errors attributable to this change.

web-player/src/lib/components/player/PlayerBar.svelte

@@ -15,7 +15,7 @@
 </script>
 
 <div
-	class="animate-enter pointer-events-auto flex items-center gap-4.5 glass-bar px-4 py-2.75 sm:hidden"
+	class="animate-enter pointer-events-auto flex items-center gap-4.5 glass-bar px-4 py-3 sm:hidden"
 >
 	<div class="min-w-0 flex-1">
 		<TrackInfo compact />
@@ -24,14 +24,14 @@
 </div>
 
 <div
-	class="animate-enter pointer-events-auto hidden items-center gap-5 glass-bar px-4 py-2.75 sm:flex"
+	class="animate-enter pointer-events-auto hidden items-center gap-5 glass-bar px-4 py-3 sm:flex"
 >
 	<div class="w-(--mf-player-side-w) min-w-0 shrink-0">
 		<TrackInfo />
 	</div>
 	<div class="flex min-w-0 flex-1 flex-col items-center gap-2">
 		<TransportControls />
-		<div class="flex w-full max-w-hero items-center gap-2.75">
+		<div class="flex w-full max-w-hero items-center gap-3">
 			<span class="min-w-8 text-right text-xs text-fg-3 tabular-nums">
 				{fmtTime(player.progress)}
 			</span>