2.3.0 — the index train: local-first recall index, incremental sweep, stemming + alias expansion

One schema-bump release (recall-index schema 3, entity-index schema 2; old
recall indexes rebuild automatically, no vault migration):

- Local-first recall index: the live BM25 index lives in the machine state dir
  (keyed by endpoint hash); capture's upkeep is a zero-network atomic file
  write, no advisory lock — replacing the O(vault) GET/PUT-whole-index round
  trip per write. The vault copy is a snapshot (sweep + session-end) used to
  seed fresh machines / catch up after another client swept
  (ECHO_RECALL_SYNC_HOURS, default 24). The read path never PUTs the vault.
- Incremental sweep: entity + recall meta carry 16-char content hashes;
  `sweep --fast` fetches only new/gone/hash-missing notes plus a rotating
  weekday shard (--all-shards forces everything); deletions drop from both
  indexes; index-only so no --apply gate. `load` auto-runs it past
  ECHO_FAST_SWEEP_DAYS (7); doctor reports index freshness. Obsidian-side
  edits now reach the indexes without manual maintenance.
- Stemming + alias expansion: echo_stem.py (conservative Porter-lite, unit-
  tested families + over-stemming guards) applied at index AND query time;
  a query fuzzy-matching an entity folds its title/alias vocabulary into the
  BM25 query at half weight — expansion can only boost docs containing the
  terms. capture hashes the note's FINAL content (auto-link reordered first).

Eval gold set 8 -> 14 queries (6 paraphrases): recall@5/MRR 1.00/1.00 vs
keyword baseline 0.75/0.79. +3 unit tests, +10 e2e; test harnesses now isolate
ECHO_STATE_DIR. All seven suites green.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

echo-memory.plugin.src/skills/echo-memory/scripts/test_echo_client.py

@@ -215,6 +215,42 @@ def test_links_create_related_section_when_absent() -> None:
     assert changed and "## Related" in new and "[[resources/concepts/beta]]" in new
 
 
+def test_stemmer_conflates_inflection_families() -> None:
+    import echo_stem
+    families = [
+        ["deploy", "deploys", "deployed", "deploying", "deployment"],
+        ["navigate", "navigation", "navigating", "navigational"],
+        ["renew", "renews", "renewing"],
+        ["prefer", "prefers", "preferring", "preferred"],
+        ["penalty", "penalties"],
+        ["saturate", "saturation", "saturated"],
+        ["frequency", "frequencies"],
+        ["expand", "expanded", "expanding"],
+        ["meet", "meeting", "meetings"],
+        ["service", "services"],
+    ]
+    for fam in families:
+        stems = {echo_stem.stem(w) for w in fam}
+        assert len(stems) == 1, f"{fam} -> {stems}"
+
+
+def test_stemmer_leaves_short_and_risky_tokens_alone() -> None:
+    import echo_stem
+    # over-stemming merges unrelated words — worse than a missed match
+    for w in ("sing", "thing", "was", "is", "bus", "this", "echo", "vault", "mpm"):
+        assert echo_stem.stem(w) == w, f"{w} mangled to {echo_stem.stem(w)}"
+    # documented non-conflations (the -al / d~s irregulars full Porter also skips)
+    assert echo_stem.stem("renewal") != echo_stem.stem("renew")
+    assert echo_stem.stem("expansion") != echo_stem.stem("expand")
+
+
+def test_content_hash_stable_and_short() -> None:
+    import echo_index as ix
+    a = ix.content_hash("hello world")
+    assert a == ix.content_hash("hello world") and len(a) == 16
+    assert a != ix.content_hash("hello world!")
+
+
 def _run_all() -> int:
     tests = [v for k, v in sorted(globals().items()) if k.startswith("test_") and callable(v)]
     failed = 0