feat(career): bundle the AXA club venue pack (career stage 2) (#963)

The Velvet Room (50 stars) now ships in every build like the bar and
arena: 4 reactive crowd loops, 2 stingers, and a balcony flyover intro
rendered from the AXA Music Stage scene (110 spectators, state-scaled
stage washes over the venue's own neon). Audio files are dive-bar
placeholders until club-scale recordings land.

The installed/delete test now asserts bundled-fallback semantics:
with every venue bundled, deleting a downloaded pack reveals the
bundled copy instead of uninstalling.

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

plugins/career/venue-packs/club/manifest.json

@@ -0,0 +1,8 @@
+{
+    "venue": "club",
+    "version": 1,
+    "loops": {"bored": "bored.mp4", "neutral": "neutral.mp4", "engaged": "engaged.mp4", "ecstatic": "ecstatic.mp4"},
+    "stingers": {"clap": "clap.mp4", "cheer": "cheer.mp4"},
+    "intro": {"video": "intro.mp4", "audio": "club-ambience.mp3"},
+    "sfx": {"up": "sfx-up.mp3", "down": "sfx-down.mp3"}
+}