feat(progression): fancy notifications for quest/path progress + completion (#552)

* feat(progression): fancy notifications for quest/path progress + completion (#551)

Surface achievement feedback as in-app toasts when the player advances or
finishes a daily/weekly quest, and when they progress or level up an
instrument path.

- progression-core.js: _diff() now emits two partial-advance events —
  quest-progressed (a still-incomplete quest whose count rose) and
  path-progressed (a challenge toward the next level completed without a
  level-up). Both are guarded so the increment that COMPLETES a quest /
  the level-up itself stays a single quest-completed / path-level-up event
  (no double toast). Period rollovers and brand-new quest ids emit nothing.
  New events added to the capability owner's declared events list.
- notifications.js (new): reusable window.fbNotify toast surface (stacked,
  animated, auto-dismiss; animation + accent via inline styles so no new
  Tailwind utilities) + progression wiring — subtle toasts for advances,
  celebratory toasts for quest completion, path level-up, and rank-up.
- index.html: load notifications.js after progression-core.
- tests: progression_progress_events (diff emission + guards) and
  progression_notifications (toast rendering + wiring) — 11 cases.

No backend change.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* fix(progression): unwrap CustomEvent .detail in notification handlers

Codex P2: window.slopsmith.on delivers a CustomEvent (bus.on →
addEventListener), so the progression payload is e.detail — not the raw
argument. All five notifications.js handlers read the arg directly, so in
the browser every field was undefined (e.g. rank-changed never toasted).
Unwrap e.detail in each handler, matching every other sm.on consumer.

The test harness masked this by invoking handlers with raw payloads; it now
wraps them as {detail: payload} like the real bus, so the unwrap is actually
exercised (the tests fail without the fix).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

static/v3/index.html

@@ -859,6 +859,7 @@
          registers the `progression` capability owner + window.v3Progression. -->
     <script src="/static/v3/theme-core.js"></script>
     <script src="/static/v3/progression-core.js"></script>
+    <script src="/static/v3/notifications.js"></script>
     <script src="/static/v3/profile.js"></script>
     <script src="/static/v3/progress.js"></script>
     <script src="/static/v3/shop.js"></script>