improved search prompt

docs/plans/search-index.md

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+# Search index + prompt display fixes
+
+Working plan. Findings come from an audit of a real `cache.db`
+(9,252 Drive nodes, 110,187 local files) on 2026-08-12.
+
+## Evidence
+
+```
+nodes                     9252
+nodes_fts                 6547     ← 2705 rows never indexed
+nodes in orphan subtrees  2705     ← exactly the missing set
+local_files              110187
+  /home/narl/go/pkg/mod   63399    (58% of the local index)
+query "test"             46405 local matches, candidate pool capped at 1000
+  top 500 by fts rank      367 (73%) from go/pkg/mod
+```
+
+`pdfs search tickets` returns only `Documents/Tickets` (My Files); the
+`tickets.pdf` sitting in the device folder `Downloads` is invisible.
+
+## P1 — 29% of Drive is unsearchable
+
+`node_is_indexable_tx` (`crates/pdfs-core/src/db/nodes.rs:606`) indexes a node
+only when the ancestor walk terminates at a row with `parent_uid IS NULL`. The
+DB holds exactly one such row (the My Files root). Device roots live in
+`device`/`sync_folder`, never in `nodes`, so every device-folder subtree
+(`Downloads`, `Pictures`, `Documents`, `Music`, `Videos` under device
+*nthinkpad*) walks up to a `parent_uid` with no row and is judged unindexable.
+Stale `pdfs-acceptance-*` roots hit the same path.
+
+- [x] Relax the rule to "the walk terminates and no ancestor is trashed",
+      keeping the existing cycle guard. A subtree whose top row's parent is
+      simply not cached is still real, reachable data.
+- [x] `MIGRATION_V21`: rebuild `nodes_fts` under the new rule, so existing
+      installs recover the missing rows instead of waiting for each node to be
+      upserted again.
+- [x] Tests: a node under an uncached parent is indexed; a trashed ancestor
+      still excludes; the migration backfills.
+
+### Found while testing: a parent cycle hangs the daemon
+
+Writing the cycle test surfaced a live defect, not a test artefact. A query
+below the trigram minimum takes the `LIKE` lane, which reads `nodes` directly
+and never consults the index, and every row it returns goes through `path_of` —
+whose parent walk is an unguarded `UNION ALL`. On a `parent_uid` cycle it never
+terminates, while holding the daemon's only SQLite connection.
+
+- [x] Depth-cap `path_of` (`db/utils.rs`), matching the 1024 cap
+      `path_relative_to` already carried.
+- [x] Depth-cap the `descendants` CTE in `upsert_node_tx`, which has the same
+      exposure on the write side.
+- [x] Keep cycles out of the index (part of the P1 rule above).
+
+Still unguarded, not touched here: `pin_is_pinned`'s ancestor walk.
+
+## P2 — local index noise crowds real files out of the candidate pool
+
+`SKIP_DIRS` (`crates/pdfs-core/src/localindex.rs:23`) misses the Go module
+cache and build output dirs. `search_v2` clamps candidates to ≤1000 and scores
+*after* SQLite, so for any common term the pool is exhausted by vendored files
+before a real one is considered.
+
+- [x] Skip `go/pkg/mod` (path-relative, not a bare name), `dist`, `build`,
+      `.cache`-style artefact dirs.
+- [x] Give `search_local_candidates` a name-prefix lane, mirroring what
+      `search_candidates` already does for Drive, so an exact-prefix match
+      cannot be starved by trigram rank.
+- [x] Tests for both.
+
+## P3 — display lies about where a hit lives
+
+- [x] `Hit::location()` (`crates/pdfs-gui/src/prompt.rs:150`) hardcodes
+      `My files / …` for every Drive hit. Derive the label from
+      `mounted_path` when the daemon resolved one (device folder, sync folder)
+      and fall back to `My files` only for the primary mount.
+- [x] Pin rows set `is_dir: pin.recursive` (`dmenu.rs:133`, `prompt.rs:872`) —
+      a non-recursively pinned folder renders and activates as a file.
+- [ ] `pdfs locations` prints `Device folder 1..5` rather than the device and
+      folder name. (Cosmetic; deferred.)
+
+## Verification
+
+Done, 2026-08-12:
+
+```
+cargo fmt --all -- --check                                  clean
+cargo clippy --workspace --all-targets -- -D warnings       clean
+cargo test --workspace --locked                             439 passed, 0 failed
+```
+
+The V21 backfill was also replayed against a read-only `.backup` of the live
+`cache.db`:
+
+```
+live_nodes         9276
+indexed            9276     (was 6547)
+downloads_subtree   300
+tickets.pdf ->     Downloads/tickets.pdf
+```
+
+That run is what caught the last defect: the backfill originally seeded an
+uncached-parent root with an empty path, so a node indexed by the migration
+(`tickets.pdf`) and the same node after a later upsert (`Downloads/tickets.pdf`)
+disagreed. The seed now keeps the name for any row that has a parent, matching
+`path_of`.
+
+Still to do, on the live system: rebuild, restart `proton-drive.service`, and
+confirm `pdfs search tickets` returns the device folder's `tickets.pdf`. The
+schema move to 21 is one-way — an older `pdfs` refuses a v21 database. The
+`local_files` shrink (~110k → ~47k) lands with the next background scan.