assets.workspace_path is INTENTIONALLY 'last-registered path' for twin
files (identical content at different paths share one asset row PK'd by
blake3 content hash). PR #146 made try_skip_unchanged document-centric;
PR #149 made reset --orphans-only document-centric; this PR removes the
last caller of get_asset_by_workspace_path (fetch.rs:193 in fetch_span,
which used it to reject PDF/audio media — for twins this could read the
wrong asset's media_type and pick the wrong branch).
Replaced with the natural 2-step lookup: get_document_by_workspace_path
(PR #146) → doc.source_asset_id → get_asset (NEW trait method, asset_id
is PRIMARY KEY so flip-flop-immune by construction).
Then removed get_asset_by_workspace_path trait method + SqliteStore impl
— 0 callers after the refactor.
UPSERT doc-comment refreshed in store.rs to make the 'last-registered'
semantics explicit so future readers don't try to 'fix' the flip-flop.
Dogfood follow-up (PR #142 1B + multi-root corpus).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
