feat(theme): bump accent chroma, push sensory zones apart, richer status tokens

Phase 10b colour push: theme reads as Magnotia, not "subdued generic dark".
Same lightness band as Phase 10a (AA preserved), more chroma across accent,
status tokens, and zone surfaces.

Dark accent: #c98555 -> #d68450 (subtle/hover/glow recomputed).
Light accent: #a06a3e -> #a3683a.
Dark status: success #7ec89a -> #5fc28a, danger #e87171 -> #e85f5f,
warning #e8c86e -> #e8be4a.
Light status: success #2f7549 -> #1f7344, danger #a83838 -> #b32626,
warning #b89a3e -> #a08a1f.

Sensory zones pushed further apart so each zone reads as its own
environment: cave cools toward blue-grey, energy warms toward red-orange,
reset cools toward green. AA on body text verified for every Card surface
in both themes.

Stale accent rgba (201,133,85) replaced with new (214,132,80) across nine
files. --shadow-accent in colors_and_type.css mirrored.

No secondary tint token added: Magnotia's identity is amber-as-the-only-
meaningful-colour. Cheaper to add a second meaningful colour later if a
real need appears than to dilute the discipline now.

Default surfaces, text tokens, and borders untouched per scope.

src/lib/components/SegmentedButton.svelte

@@ -8,7 +8,7 @@
       class="rounded-lg font-medium
         {size === 'small' ? 'px-2.5 py-1 text-[11px]' : 'px-3.5 py-[6px] text-[12px]'}
         {value === option
-          ? 'bg-accent text-bg shadow-[0_1px_4px_rgba(201,133,85,0.3)]'
+          ? 'bg-accent text-bg shadow-[0_1px_4px_rgba(214,132,80,0.3)]'
           : 'text-text-secondary hover:text-text hover:bg-hover'}"
       style="transition-duration: var(--duration-ui)"
       onclick={() => value = option}