Create panel: wire chapters into the engine

[mehdibha]

Tracks wiring the panel-lab drill-in panel — now mounted as /create's real panel (PR #664) — into the create engine, chapter by chapter. One short-lived PR per chapter, merged to main.

Ground rules (also in CLAUDE.md):

• The panel schema (www/src/modules/panel-lab/state.ts) is the source of truth. Wiring a chapter = making the engine/preview/export respond to its axes: reuse engine machinery where an axis matches, change the engine where it diverges, build the mechanism where it's new. Never bend the panel to old engine params.
• A chapter carries a WIP chip until its values actually drive the preview and export; the chip drops in the PR that wires it.
• The old panel (www/src/modules/create/panel/, unmounted) holds working wiring logic — mine it per chapter, delete what's absorbed in the same PR.
• New axes are still product decisions: propose before implementing.

Done in #664: header controls (PresetPicker switcher, reset, ⌘P search, Save/Export), Origin as the first-time default, drill-in animation, motion tweaks.

Next: chapter skeleton — every chapter mounted with a WIP chip.

Chapters

Identity

• Color
• Typography
• Icons
• Shape
• Space
• Surfaces

Page chrome

• Cursor
• Selection
• Scrollbars

Component states

• Focus
• Invalid
• Disabled
• Motion

Components

• Buttons (incl. groups, toggles, segmented control)
• Inputs (incl. groups, number field, OTP)
• Switch
• Checkbox
• Radio
• Choice cards
• Pickers
• Calendar
• Sliders
• Menus
• Dialogs
• Popovers
• Tooltips
• Links
• Tabs
• Breadcrumbs
• Pagination
• Notices
• Skeleton
• Spinner
• Progress
• Badges
• Kbd
• Avatars
• Tables
• Accordion
• Charts

Parity bar (when the last chip drops)

All chapters wired, save/export round-trips the full schema, mobile sheet verified — then delete the remaining modules/create/panel/ leftovers.

[mehdibha]

Chapter skeleton done in #664 (4467591): all chapters mounted with WIP chips inline after their titles, on index rows and the drilled-in header. Chips drop per chapter via panel-lab/wired.ts. Next: wire chapters, highest-leverage first (Color, Typography, Shape).