Settings: grouped cards, short subtexts and Find a setting #292

Rebuild Prism's Settings on the shared core components that shipped in prism-term-core core-v0.25.0 (pinned since #291), so both apps' settings look and read the same.

Owner, 2026-10-05: approved the "Grouped cards" design (v1) with one change, no accent bar on the chosen rail item, and accepted all recommendations Q1 to Q6 of the spec and plan.

What this covers (spec section 3.3, PR 2):

• Pages: Appearance, Explorer, Terminal, Agents, Dictation, Media, About, plus Find a setting at the top of the rail.
• Every row: an icon, a label and one short subtext (at most 8 words) that carries live state.
• Sections as headed panels; the chosen rail page is a grey fill, not the accent.
• Prism's own copies of the controls go; the core's are used.
• Media merges Visualizer and Progress bar behind a header switch; About gets Version.
• No storage key changes; every behaviour unchanged.
• Gate scenarios (termOptions, termColourPicker, dictationPage, ...) follow the new labels; new settingsLook and settingsSearch e2e, settingsLook in e2e:terminal.

Spec and plan: research/prism/2026-10-05-settings-no-subtext/2026-10-05-settings-redesign-spec-and-plan.md (copied into PrismTerminal as docs/superpowers/specs/2026-10-05-settings-redesign-design.md).
Prism Terminal side: Maxaubert/PrismTerminal#135.