* feat(projects): search shelf documents by keyword
Add search_project_documents: two-tier name/summary then bounded content scan, case-insensitive substring matching with original-text offsets. Never converts on the fly; reports stop_reason, content_scanned, skipped reasons, and capped unscanned/truncated ids.
* fix(projects): derive unscanned count without paging after budget trip
Review feedback: once the content budget trips, stop paging list_active to enumerate unscanned ids — cap ids at the trip page and derive the honest total from one count_active query (tier 1 is exhaustive, so active - tier1 hits - processed = unscanned). Also add a tool-level isolation test pinning that search never crosses projects or users.
* fix(projects): scan the shelf over one stable snapshot, not offset pages
Review feedback: offset paging re-read the live shelf per page, so a concurrent upload/trash between pages could duplicate a match or silently skip one while still claiming complete coverage. Tier 1 now materializes the whole shelf in a single SELECT (one read snapshot) and tier 2 iterates those same rows; the budget-trip unscanned count is derived exactly from the snapshot with no extra query. Mid-scan upload/trash regression tests pin both failure modes.
