docs: scrub dangling references to deleted roadmap docs

The ROADMAP/ROADMAP-PINCHFLAT docs were removed; this drops the now-dead
"see ROADMAP-PINCHFLAT.md" breadcrumbs (and one "the roadmap" mention)
from source comments, preserving the surrounding Pinchflat-style context.
Comment-only; typecheck (node+web) green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/main/sources.ts

@@ -1,9 +1,8 @@
 /**
- * Persistence for the media-manager index (Pinchflat-style; see
- * ROADMAP-PINCHFLAT.md). Two plain-JSON stores in userData, mirroring the
- * history.ts pattern (and the same deliberate choice to stay on JSON rather than
- * better-sqlite3 -- revisit if a user indexes many large channels, see the
- * Phase H risk note in the roadmap):
+ * Persistence for the media-manager index (Pinchflat-style). Two plain-JSON
+ * stores in userData, mirroring the history.ts pattern (and the same deliberate
+ * choice to stay on JSON rather than better-sqlite3 -- revisit if a user indexes
+ * many large channels):
  *
  *   sources.json      -- one Source record per added channel/playlist
  *   media-items.json  -- every MediaItem across all sources (queried by sourceId)