feat(career): profile passport wall, home career card, shareable PNG card (#955)

* feat(career): profile passport wall, home career card, shareable PNG card

Career v3, WS2. The identity artifact leaves the plugin tab:

- Profile: #v3-profile-passports-mount (core, one div) filled by career
  on v3:profile-rendered — per-instrument shelves of earned covers,
  hours, gig count, open-career link. Absent-not-empty.
- Home: the plugin-count stat tile becomes #v3-dash-career-slot with the
  old stat as fallback content; career replaces it with a trading-card
  tile (leather + foil shine, badge count, hours, closest-stamp ask) on
  the existing v3:dashboard-rendered event.
- Shareable card: static/js/blob-io.js (downloadBlob lifts the idiom
  duplicated verbatim in settings-io/diagnostics-export — both
  refactored; copyImageBlob wraps ClipboardItem, returns false to signal
  the download fallback). Earned passports get Save/Copy card: a
  natively-drawn 480×640 canvas (leather, stamp ring, stubs+hours line);
  copy falls back to download with a notice when the clipboard refuses.
- Mount-point convention documented in docs/plugin-v3-ui.md.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* fix(career): external surfaces stay absent until a passport exists

CodeRabbit on #955: a bare commitment produced a zero-passport wall and
replaced the dashboard fallback. Docs also now say mounts may hold
fallback content and plugins REPLACE, never append.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

---------

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

plugins/career/tests/passports.test.js

@@ -150,3 +150,30 @@ test('ppFillFraction: song progress toward the bar, in-progress only', () => {
     assert.equal(ppFillFraction(p('in_progress', 3, 0)), 0);   // no bar → no fill
     assert.equal(ppFillFraction(null), 0);
 });
+
+test('careerTotals / wall + dash card stay absent without commitment', () => {
+    const w = load();
+    const t = w.__careerPassportTest;
+    // No _pp at all → null; committed-less view → null (absent-not-empty).
+    assert.equal(t.careerTotals(), null);
+    t.setView({ config: { instruments: ['guitar'] },
+        instruments: { guitar: { committed_at: null, passports: [] } } });
+    assert.equal(t.careerTotals(), null);
+    // Committed but zero passports opened: still absent (no zero-wall).
+    t.setView({ config: { instruments: ['guitar'] },
+        instruments: { guitar: { committed_at: 'x', passports: [] } } });
+    assert.equal(t.careerTotals(), null);
+    // Committed with an earned badge + hours → totals aggregate.
+    t.setView({ config: { instruments: ['guitar', 'bass'] },
+        instruments: {
+            guitar: { committed_at: 'x', passports: [
+                { badge: 'earned', seconds_total: 3600, genre: 'Blues', genre_key: 'blues' },
+                { badge: 'in_progress', seconds_total: 120, genre: 'Funk', genre_key: 'funk',
+                  qualifying_count: 4, requirement: { songs: 5, min_stars: 2 } }] },
+            bass: { committed_at: null, passports: [] },
+        } });
+    const totals = t.careerTotals();
+    assert.equal(totals.badges, 1);
+    assert.equal(totals.seconds, 3720);
+    assert.equal(totals.walls.length, 1);
+});