fix(career): gig song selection — full-genre pool, working re-roll, and the venue pack loads (#976)

* fix(career): a gig's song pool is the whole genre, and re-roll varies it

Two tester reports, one root: the gig song pool was built from only two sets —
songs played ON THIS PASSPORT'S INSTRUMENT, and songs never played AT ALL
(`filename NOT IN song_stats`).

A song played on a DIFFERENT instrument's arrangement is in neither: it has a
stats row (so the "unplayed" filler skipped it), and its played bucket is that
other instrument's, not this passport's. It could never be gigged.

- "Metalcore says 137 songs only shows 1 in the gig list" — a library of
  metalcore all played on another instrument. Reproduced: a guitar passport with
  137 bass-played metalcore songs got a 404, zero songs. The "1" the tester saw
  was whatever handful happened to be on-instrument or truly unplayed.

- "Passport re-roll does not change songs" — a set drawn from that filler was the
  library's first N in table ORDER, every call. Re-roll re-proposes, so it
  returned the identical set. Reproduced: 3 proposals, byte-identical.

_unplayed_genre_songs -> _fill_genre_songs: the pool is now every library song of
the genre the set hasn't already picked (a stats row on some other instrument has
no bearing on whether a song can be in THIS gig), and it is shuffled so re-roll
actually re-rolls.

Both reproduced against the real propose logic before the fix and pinned as
regression tests (both fail on the pre-fix routes.py). Full career suite green.

* fix(career): load the gig's venue pack when the gig starts

Tester: "Venue doesn't load when starting song from passport. Loads standard
particles."

crowd.setManifest(venue) — the call that actually loads a venue's crowd/stage
pack — is reached ONLY through pushCrowdManifest, and pushCrowdManifest is
called ONLY from refresh(), the career tab's own reload. A gig navigates AWAY
from the career tab to the player, so refresh() never runs during it. startGig
set the venue override and nulled _appliedManifestVenue but never re-pushed, so
the venue visualization turned on (3D highway) while its pack never loaded — the
song played over the bare highway backdrop, or over whatever venue a previous
refresh() had left applied.

startGig now pushes the crowd manifest for the gig venue right after setting the
override, using the career state the booking screen already fetched.

This is a call-graph fact, not a guess (pushCrowdManifest has exactly one other
caller and startGig is not it), but it is fixed by static analysis — I could not
reproduce the user-visible symptom locally because this instance happened to have
a manifest already applied from a prior refresh. On-device confirmation on a real
passport gig is still owed.

Guard test: startGig must push the manifest after setting the override (fails on
the pre-fix source). Career suite green.

plugins/career/screen.js

@@ -1192,7 +1192,21 @@
                 if (typeof window.setViz === 'function') window.setViz('venue');
             } catch (_) { /* viz optional — restore stays intact */ }
         }
+        // Push the gig's venue pack to the crowd layer NOW.
+        //
+        // crowd.setManifest(venue) is reached only through pushCrowdManifest,
+        // and pushCrowdManifest is called only from refresh() — the career
+        // tab's own reload. A gig navigates AWAY from the career tab to the
+        // player, so refresh() never runs during it, and setting the override
+        // above does nothing on its own. The result the testers saw: the venue
+        // visualization turns on (3D highway) but its crowd/stage pack never
+        // loads, so the song plays over the bare highway backdrop ("standard
+        // particles"), or over whatever venue a previous refresh() happened to
+        // leave applied. We just changed the override to this gig's venue, so
+        // re-push for it. _state is the career state the booking screen already
+        // fetched; guard for the rare null.
         _appliedManifestVenue = null;
+        if (_state) pushCrowdManifest(_state);
         _ppGigRun = {
             songs: prop.songs,
             venue_id: prop.venue_id,