feat: audit phase 6 (T1) — persistent HUD, skip intro, faster entrance

The audit's headline UX finding, measured on production: cold load showed a
black screen for ~5s, then a wordless constellation. At 9 seconds the number
of words on screen was zero — no name, no title, no hint that anything was
clickable. A recruiter could not learn one fact without clicking.

- New Hud.svelte: name, market-legible title and a one-line hook, always on
  screen, sourced from the origin node. Readable at ~1s instead of never.
  Added `tagline` to OriginNode so it lives with the rest of the content.
- New CoachHint.svelte: first-run "drag / scroll / click" hint. The icons
  gave no affordance that the tree was interactive at all.
- Skip intro control. runEntranceAnimations now returns a handle whose skip()
  enumerates the entrance's own nested GSAP context and calls progress(1) on
  each finite tween — which fires their onComplete, so node interactivity and
  the ambient pulses come up exactly as if the intro had played through.
  Verified: a node is clickable immediately after skipping.
- Returning visitors land on the settled tree (localStorage), reusing the
  same code path as reduced motion. The flag is set once the intro has
  actually been seen, not at mount — otherwise someone who bounced after a
  second would be marked as having seen it and never get it.
- Entrance timings cut: title 2.5s -> 1.6s, zoom 4.5s -> 2s, stagger 0.08 ->
  0.045 (that last one was 4.5s of cascade on its own across 56 nodes).

Two bugs found while building this:
- animation.ts hardcoded its timings as literals instead of reading
  config.ts TIMINGS, so editing config silently did nothing. Now derived.
- Skip and the coach hint were timed off a magic 3200ms, so Skip vanished
  while the intro was still running and "Click a node" appeared before the
  nodes did. Both now derive from the entrance's real computed length, which
  the handle exposes as durationMs.
- Skip sat bottom-right underneath the service-worker update toast (same z
  token, later in DOM order). Moved to bottom-centre; the toast got its own
  layer token.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/app.css

@@ -59,6 +59,7 @@
 	--z-panel-toggle: 950;
 	--z-modal: 1000;
 	--z-toast: 1100;
+	--z-update-toast: 1150;
 	--z-tree-nav: 1200;
 	--z-skip-link: 2000;