feat(memory-b): port V2 non-exact fusion weights

Also clear three stale counts the release train authorised: criteria A1
wording (sync + hybrid), criteria G1 counts (173/12), README test-site count.

README.md

@@ -250,7 +250,7 @@ recallBlocksHybrid(store, embedder, query, opts)  // async wrapper
 ```
 
 Why the split rather than "make recallBlocks async": every existing caller keeps
-calling a sync function, so the 9 test call sites and the whole phase-A surface
+calling a sync function, so the existing test call sites and the whole phase-A surface
 need no edit, and the golden fixture proves the sync path did not move.
 
 With no embedder (or a failing one) the wrapper is exactly `recallBlocks`, and it

docs/phase-b-criteria.md

@@ -143,7 +143,7 @@ return ""
 
 | # | 断言 | 依据 |
 |---|---|---|
-| A1 | `recallBlocks` 改为 `async` 后，phase A 的 26 个测试与 8 个 checkpoint **全部仍然通过**，一条不改语义 | 现在 `agent/pre-step` handler 已经是 `async`（`lib/index.js` 的 `toggle`），所以异步化不破坏调用方 |
+| A1 | `recallBlocks` 保持同步，另新增异步 `recallBlocksHybrid`；phase A 的 26 个测试与 8 个 checkpoint **全部仍然通过**，一条不改语义 | 现有调用方保持同步，异步只出现在新 wrapper |
 | A2 | 未配置 embedder 时，`recallBlocks` 的返回与 phase A **逐字节相同**（同序、同分、同 `why`） | 无向量是合法配置，不是降级 |
 
 **A1 变异**：把 `recallBlocks` 改回同步并在内部 await 一个 Promise ⇒ 测试红（语法/类型层面即失败）。
@@ -319,7 +319,7 @@ phase B 必须把向量放进 **[0..1) 带**，不得越到 exact 带。
 
 | # | 断言 |
 |---|---|
-| G1 | phase A 的 26 测试 + 8 checkpoint **全绿**，语义不变（A1/A2 已覆盖） |
+| G1 | phase A 的 173 tests + 12 checkpoints **全绿**，语义不变（A1/A2 已覆盖） |
 | G2 | 未配置 embedder ⇒ 进程内无任何 HTTP 出站、无新依赖被加载 |
 | G3 | `stablemem_commit` 在 embedder 不可用时**仍能写入**（块入库、vector 留空，`no_vector` 计数 +1），不报错 |
 | G4 | 不引入 media/媒体块（`docs/feasibility.md` §5.4 的决定不变） |

lib/recall.js

@@ -407,9 +407,16 @@ export function recallBlocks(store, query, { topK = 5, poolSize = 50, fingerprin
     const exactScore = vectorScores instanceof Map
       ? 1.0 + (vectorScores.get(candidate.id) ?? 0) * 0.01
       : 1.0 + candidate.lexical * 0.01 + boundaryBonus * 1e-4
+    // Ported from Go: internal/memory/fusion.go:61-66 and :430-434.
+    // Non-exact candidates use vector*0.7 + symbol*0.3. A missing vector score
+    // is the symbol-only fallback and must not invent a vector contribution.
+    const hasVectorScore = vectorScores instanceof Map && vectorScores.has(candidate.id)
+    const vectorScore = hasVectorScore ? vectorScores.get(candidate.id) : 0
     const score = exact
       ? exactScore
-      : nonExact + boundaryBonus * 1e-3
+      : vectorScores instanceof Map && hasVectorScore
+        ? vectorScore * 0.7 + nonExact * 0.3
+        : nonExact + boundaryBonus * 1e-3
     scored.push({
       id: candidate.id,
       text: candidate.text,

test/phase-b-a.test.js

@@ -369,3 +369,80 @@ test('V1†: folding an exact hit into a weighted sum turns V1 red', async (t) =
     } finally { store.close() }
   } finally { rmSync(dir, { recursive: true, force: true }) }
 })
+
+// ── V2: non-exact records combine vector*0.7 + symbol*0.3 ───────────────
+//
+// Ported from Go `internal/memory/fusion.go:61-66` (defaultWeights) and
+// `:430-434` (the non-exact weighted sum). V2 scores records that are ALREADY
+// in the symbol pool: appending symbol-only records is V5, and the asymmetric
+// MinScore gate is V5's too — neither is opened here.
+//
+// ★ The criterion below is shared verbatim by the positive case and the mutant,
+// so a mutant can only pass by satisfying the same requirement. The V1† lesson
+// was that re-writing the requirement inside the mutant's body tests the mutant,
+// not the code.
+function assertV2Weights(recall, store) {
+  // A query from the fixture corpus that yields non-exact records. `QQ 插件`
+  // does not: FTS returns nothing for it, so the assertion has no subject.
+  const query = '分机号'
+  const plain = recall(store, query, { topK: 5 })
+  const candidate = plain.find((hit) => hit.exact === false)
+  assert.ok(candidate, `precondition: a non-exact record exists for ${query}`)
+  const pick = (score) => recall(store, query, { topK: 5, vectorScores: new Map([[candidate.id, score]]) })
+    .find((hit) => hit.id === candidate.id)
+  const zero = pick(0)
+  const one = pick(1)
+  assert.ok(zero && one, 'the scored record must remain in the candidate pool')
+  // Go: f.Score = f.VectorHit*w.Vector + f.SymbolHit*w.Symbol with Vector = 0.7.
+  assert.equal(one.score - zero.score, 0.7,
+    'vector 0→1 must move the fused score by exactly Go Vector weight 0.7')
+  // The symbol term must still be present: with no vector score the record keeps
+  // its symbol-only score rather than collapsing to 0 (Go's `SymbolHit*w.Symbol`).
+  const noMap = recall(store, query, { topK: 5 }).find((hit) => hit.id === candidate.id)
+  const emptyMap = recall(store, query, { topK: 5, vectorScores: new Map() })
+    .find((hit) => hit.id === candidate.id)
+  assert.equal(emptyMap.score, noMap.score, 'a missing vector score must not invent a contribution')
+}
+
+test('V2: a non-exact record uses the Go 0.7/0.3 weighted score', () => {
+  const store = seededStore()
+  try {
+    assertV2Weights(recallBlocks, store)
+  } finally {
+    store.close()
+  }
+})
+
+test('V2†: changing the Go weights to 0.5/0.5 bites the unchanged criterion red', async (t) => {
+  const { readFileSync, writeFileSync, mkdtempSync, rmSync, cpSync } = await import('node:fs')
+  const { tmpdir } = await import('node:os')
+  const { join } = await import('node:path')
+  const { fileURLToPath, pathToFileURL } = await import('node:url')
+  const libDir = fileURLToPath(new URL('../lib/', import.meta.url))
+  const pkgRoot = fileURLToPath(new URL('..', import.meta.url))
+  const dir = mkdtempSync(join(tmpdir(), 'mv2-'))
+  try {
+    cpSync(libDir, join(dir, 'lib'), { recursive: true })
+    cpSync(join(pkgRoot, 'package.json'), join(dir, 'package.json'))
+    const target = join(dir, 'lib', 'recall.js')
+    let source = readFileSync(target, 'utf8')
+    const anchor = 'vectorScore * 0.7 + nonExact * 0.3'
+    assert.equal(source.split(anchor).length - 1, 1, 'M-V2 anchor must occur exactly once')
+    source = source.replace(anchor, 'vectorScore * 0.5 + nonExact * 0.5 // MUTATED: weights')
+    writeFileSync(target, source)
+
+    const mod = await import(pathToFileURL(target).href)
+    const store = seededStore()
+    try {
+      assert.throws(() => assertV2Weights(mod.recallBlocks, store), (err) => {
+        assert.equal(err.code, 'ERR_ASSERTION', 'only the criterion may bite')
+        t.diagnostic(`V2† RAW RED >>> ${String(err.message).split('\n')[0]}`)
+        return true
+      }, 'M-V2 must break the unchanged V2 criterion')
+    } finally {
+      store.close()
+    }
+  } finally {
+    rmSync(dir, { recursive: true, force: true })
+  }
+})