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>

CHANGELOG.md

@@ -7,6 +7,19 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+- **Career on the Profile and Home pages** — the Profile gains a passport
+  wall (earned-badge covers per instrument, hours, gig count; absent until a
+  passport exists), injected through the same mount-point + rendered-event
+  seam the achievements plugin uses (now documented in docs/plugin-v3-ui.md).
+  The home page's plugin-count stat tile becomes a career trading card
+  (badges, hours, the closest stamp ask, foil shine) with the old stat as the
+  built-in fallback when career has no state. Earned passports gain **Save
+  card / Copy card** — a natively-drawn PNG passport card, downloadable or
+  copied straight to the clipboard for pasting outside the app (shared
+  `blob-io` helpers replace the download idiom previously duplicated in
+  settings-io and diagnostics-export).
+
 ### Changed
 - **The full mix is a stem** (#933) — core no longer depends on `original_audio:`, a
   top-level manifest key this repo invented (#583) that the feedpak spec never had.