feat(frontend): redesign publish agent flow modal (#13006)

## Why
The existing publish-agent modal was visually inconsistent with the rest
of the platform: a dense card layout, no progress signal between its
three steps, and no transitions. Step 2 (listing) was an unstructured
long form and step 3 (review) was a heavy preview panel. This PR
redesigns the entire flow to fit our design system and adds polished
step transitions.

## What
- New persistent stepper (`StepStrip`) with animated number → check
transition and connector progress fill.
- Shared `StepFooter` for consistent secondary/primary buttons across
steps.
- **Agent select**: two-column rounded list, purple selection state,
selection radio (no fake thumbnails).
- **Listing form**: single-open accordion (Listing basics / Thumbnails /
Experience details) with phosphor icons + per-section completion check
(purple) and validation warning (rose). Title-tooltips on every
input/select. Recommended-schedule trigger styled like an input. Compact
thumbnail strip.
- **Review step**: edge-to-edge purple gradient + blur orb (via portal
so it reaches dialog corners), animated tick with pulsing rings,
confetti, "What happens next" timeline, and `Go to Creator Dashboard`
CTA.
- Direction-aware slide transitions between steps, height auto-animates,
respects `prefers-reduced-motion`.
- Reusable additions to design-system atoms: `labelVariant`,
`labelClassName`, `labelTooltip` props on `Input` and `Select`. Default
`Input`/`Select` border radius reduced from `rounded-3xl` to
`rounded-xl`.

## How
- `PublishAgentModal` now owns the persistent `StepStrip` and wraps the
active step in `AnimatePresence` (`mode="wait"`) with direction-aware
variants. The wrapper uses `motion.div layout` so dialog body height
interpolates instead of jumping.
- Each step component (`AgentSelectStep`, `AgentInfoStep`,
`AgentReviewStep`) was rebuilt to use design-system atoms/molecules, the
new `StepFooter`, and Framer Motion (tween / ease-out / under 300 ms per
Emil Kowalski's animation principles).
- `AgentReviewStep` uses `react-dom`'s `createPortal` to render its
gradient + blur into the dialog's `[data-dialog-content]`, escaping the
scroll wrapper's `overflow-x-hidden` without modifying the shared
`Dialog` molecule.
- Added a 320 ms delayed open of the first accordion in `AgentInfoStep`
so the slide-in completes before the section unfolds.
- Playwright assertions in `marketplace.page.ts` updated to match the
new copy ("Pick the saved agent version…", "Continue").



https://github.com/user-attachments/assets/9089c76a-f25d-4f3a-8535-ff41b1c10066


## Test plan
- [x] Open Publish flow from `/settings/creator-dashboard` and verify
the stepper animation forward & back across all three steps.
- [x] Select agent → list shows two columns; selected card uses purple
ring + radio.
- [x] Step 2: validate accordion open one-at-a-time, completion ticks,
validation warnings, tooltips, single-line textareas, schedule button
styling, thumbnails strip.
- [x] Submit → review step shows gradient banner, tick with pulsing
rings, confetti, timeline, and footer buttons.
- [ ] Verify focus rings are not clipped inside accordions.
- [ ] Verify `prefers-reduced-motion` collapses animations to opacity
swaps.
- [ ] Existing Playwright marketplace publish flow passes with updated
copy.