fix: A1-14 real neural embeddings via Bumblebee multilingual-e5-small with Float32 BLOB vector cache

SPECGAPS.md

@@ -23,7 +23,8 @@ Gap categories: **SC** = spec correct, fix code | **CS** = code correct, update
 | A1-11 | ~~Graceful shutdown with inflight request tracking~~ | preview.allium:47-48 | `stop_preview` now closes the listener, parks the reply, and drains monitored inflight request tasks before reporting stopped | **Resolved:** acceptor transfers socket ownership to each request task; GenServer monitors inflight tasks, `begin_graceful_stop` stops accepting and finalizes via `:DOWN`/`:drain_timeout` (5s force-kill cap), 1 test added |
 | A1-12 | ~~Real Pagefind integration for search~~ | generation.allium:208 | Functional client-side search: `PagefindUI` defined in bundled `pagefind-ui.js`, fragment index records url/title/body-scoped text per page, search-runtime wires it up | **Resolved:** bundled real `PagefindUI` (fetch index, ranked full-text match, highlighted excerpts) + `pagefind-ui.css` as local assets read into `Pagefind`; index scoped to `data-pagefind-body` (unmarked pages excluded per PagefindHtmlMarking), title from `<title>`/`<h1>`; localized "No results found" label via `data-search-no-results` (de/fr/it/es); 3 unit tests added |
 | A1-13 | ~~Git sidebar shows only "Working tree" placeholder~~ | sidebar_views.allium:651-770 | `git_view/1` now builds a full `layout: "git"` view from `BDS.Git` (repository/remote_state/status/history); `SidebarComponents` renders active + not_a_repo states | **Resolved:** `git_view/1` in sidebar.ex assembles branch/upstream/ahead/behind, status files, paginated history (20/page); `render_git_sidebar` renders branch header, sync legend, fetch/pull/push/prune-lfs buttons, commit form, clickable status files (open git_diff), history entries; shell_live wires `git_commit` (closes git_diff tabs), `git_fetch`/`git_pull`/`git_push`/`git_prune_lfs`, `git_initialize`; `BDS.Git.history` enriched with author/date, `BDS.Git.set_remote/2` added; i18n for de/fr/it/es; 3 shell tests + git author/date assertions added |
-| A1-14 | Embedding uses TF-IDF hash projection instead of real neural model | embedding.allium:44-53, invariants ModelCaching/VectorCacheInDb | `backends/in_app.ex` hashes terms into sparse vectors via `:erlang.phash2`; no ONNX model, no `"query: "` prefix, no mean pooling, vectors stored as JSON text not Float32Array BLOB, snapshot-based neighbor lookup instead of USearch HNSW index | Fix code: (1) add Bumblebee + ONNX runtime deps to run `Xenova/multilingual-e5-small`, (2) implement lazy model download + cache in app data dir, (3) `"query: "` prefix + mean pooling + L2 norm in backend, (4) store vectors as binary BLOB (1536 bytes), (5) replace JSON snapshot with USearch HNSW index (cosine, M=16, ef=128/64, 5s debounce), (6) cross-language semantic similarity must work |
+| A1-14 | ~~Embedding uses TF-IDF hash projection instead of real neural model~~ | embedding.allium:44-53, invariants RealNeuralModel/ModelCaching/VectorCacheInDb | `Backends.Neural` runs `intfloat/multilingual-e5-small` (e5 weights behind the Xenova id) via Bumblebee+EXLA | **Resolved (core):** added bumblebee/nx/exla deps; `Backends.Neural` is a lazily-loaded GenServer that builds the Bumblebee text-embedding serving on first request (`"query: "` prefix + mean pooling + L2 norm), downloads+caches the model under the app data dir (ModelCaching), and is wired into the supervision tree when configured; vectors now persisted as packed little-endian Float32 BLOB (384×4=1536 bytes) instead of JSON text (VectorCacheInDb) with migration recreating `embedding_keys.vector` as BLOB; `InApp` demoted to documented offline/test stub; test config uses the stub so the suite stays offline; spec EmbeddingModel clarified (Xenova id ↔ intfloat weights via Bumblebee); 3 tests added (BLOB round-trip + Neural model_info/behaviour). **Deferred to A1-14b:** USearch HNSW index. |
+| A1-14b | USearch HNSW ANN index + debounced persistence not implemented | embedding.allium:75-87 (config), FindSimilar, invariant DebouncedPersistence | Neighbor lookup still uses the JSON cosine snapshot (`Embeddings.Index`), not a USearch HNSW index; no 5s debounced index persistence (snapshot rebuilt synchronously) | Fix code: replace JSON snapshot with USearch HNSW index file (`embeddings.usearch`, cosine, M=16, efConstruction=128, efSearch=64), label→post_id mapping, 5s debounced save + force-save on project switch/shutdown |
 | A1-15 | ~~Preview vs generation content source strategy undocumented~~ | preview.allium (no invariant), generation.allium (no invariant) | Generation uses only published .md file content (`Generation.Data` snapshots set `content: nil`); preview includes published+draft posts and prefers DB content over file (`Preview.Router` queries `:published`/`:draft`, uses `editor_body`) | **Resolved:** added `PreviewDraftOverlay` invariant to preview.allium and `GenerationPublishedOnly` invariant to generation.allium; both cross-reference each other; code already correct, 3 tests added for draft-in-preview behavior |
 
 ### A2. Spec Should Update (code is normative)
@@ -184,7 +185,7 @@ All reconciled to follow code. Specs must be self-consistent and match code.
 
 ## Priority Order for Resolution
 
-1. **A1-1 through A1-14** — code must follow spec (includes auto-save, on-demand preview, template lookup, validation gates, real Pagefind, graceful shutdown, real embedding model)
+1. **A1-1 through A1-14b** — code must follow spec (includes auto-save, on-demand preview, template lookup, validation gates, real Pagefind, graceful shutdown, real embedding model; A1-14b = USearch HNSW index still open)
 2. **D1-1 through D1-18** — untested invariants/guarantees
 3. **C-1 through C-3** — internal spec inconsistencies (reconcile to code)
 4. **B1-1 through B1-6** — major code behaviors missing from spec