fix: PR-2 memory plugin behavior improvements

## Task 5: Canonical exact dedupe
- Already implemented in PR-1 with enforceLongTermLimits()
- Source priority: explicit > manual > compaction
- Same source: higher confidence wins

## Task 6: Structured negative guard
- Add isNegatedMemoryRequest() for adjacency detection
- "不要記住" / "don't remember" are now properly ignored
- "not forget to remember" no longer false positive (not a directive)
- Restrict patterns to line-start (^|\n) to avoid mid-sentence matches

## Task 7: Compaction quality gate
- Add shouldAcceptWorkspaceMemoryCandidate() predicate
- Reject low-quality candidates: git hashes, errors, stack traces
- Reject temporary progress, code signatures, path-heavy facts
- Only accept entries with >= 20 chars

## Pattern improvements
- All patterns use matchAll() with proper g flag
- Dedupe by canonical text in extractExplicitMemories()
- Line-start anchor prevents "to remember" mid-sentence matches
- Add more trigger patterns: save/add to memory, commit to memory

Tests: 36 passing

src/extractors.ts

@@ -10,22 +10,68 @@ function hash(value: string): string {
   return createHash("sha1").update(value).digest("hex").slice(0, 12);
 }
 
+/**
+ * Check if a memory request is negated (e.g., "不要記住", "don't remember").
+ * Uses structured adjacency detection to avoid false positives.
+ */
+function isNegatedMemoryRequest(text: string, matchIndex: number): boolean {
+  const prefix = text.slice(Math.max(0, matchIndex - 30), matchIndex);
+
+  // Chinese negative: 不要/別/不用 + optional 幫我, must be adjacent to trigger
+  if (/(?:不要|別|别|不用|不需要|勿)\s*(?:幫我|帮我)?\s*$/u.test(prefix)) {
+    return true;
+  }
+
+  // English negative: do not / don't / never / not + optional please, must be adjacent to trigger
+  if (/(?:do\s+not|don't|dont|never|not)\s+(?:please\s+)?$/i.test(prefix)) {
+    return true;
+  }
+
+  return false;
+}
+
 export function extractExplicitMemories(text: string): LongTermMemoryEntry[] {
+  // 注意：所有pattern必須有 g flag，因為使用 matchAll()
+  // Pattern 必須在行首匹配，避免匹配到句子中間的非指令式用法
   const patterns = [
-    // 注意：所有pattern必須有 g flag，因為使用 matchAll()
-    /(?:请记住|記住|记住这一点|remember this|commit to memory)[:：]?\s*(.+)$/gim,
+    // 中文：請/幫我 + 記住 + 可選後綴
+    /(?:^|\n)\s*(?:请|請)?(?:帮我|幫我)?(?:记住|記住)(?:这一点|這一點|这点|這點|这个|這個)?[:：,，]?\s*(.+)$/gim,
+    // 英文：remember this/that - 必須在行首，避免 "to remember" 非指令匹配
+    /(?:^|\n)\s*(?:please\s+)?remember\s+(?:this|that)?[:：,，]?\s*(.+)$/gim,
+    // save/add to memory
+    /(?:^|\n)\s*(?:please\s+)?(?:save|add)\s+(?:this|that)?\s*(?:to|in)\s+memory[:：,，]?\s*(.+)$/gim,
+    // commit to memory
+    /(?:^|\n)\s*(?:please\s+)?commit\s+(?:this|that)?\s*to memory[:：,，]?\s*(.+)$/gim,
+    // going forward / from now on
     /(?:从现在开始|從現在開始|从今以后|從今以後|from now on|going forward)[:：,，]?\s*(.+)$/gim,
+    // 偏好
+    /(?:我的偏好是|我偏好|以后请|以後請|以后都|以後都)[:：,，]?\s*(.+)$/gim,
+    /(?:^|\n)\s*(?:my preference is|i prefer)[:：,，]?\s*(.+)$/gim,
   ];
 
   const now = new Date().toISOString();
   const entries: LongTermMemoryEntry[] = [];
+  const seen = new Set<string>();
 
   for (const pattern of patterns) {
     for (const match of text.matchAll(pattern)) {
       const body = match[1]?.trim();
       if (!body || body.length < 8) continue;
+      
+      // Calculate actual trigger position (after possible newline)
+      const triggerIndex = match.index! + (match[0].match(/^[\s\n]*/)?.[0]?.length || 0);
+      
+      // Check if this is a negated request (e.g., "不要記住")
+      if (isNegatedMemoryRequest(text, triggerIndex)) continue;
+      
+      // Check if it's a deferral (e.g., "later", "next time")
       if (/^(再说|再說|later|next time)$/i.test(body)) continue;
 
+      // Dedupe by canonical body
+      const key = body.toLowerCase().replace(/\s+/g, " ").trim();
+      if (seen.has(key)) continue;
+      seen.add(key);
+
       const type = classifyExplicitMemory(body);
       entries.push({
         id: id("mem"),
@@ -137,6 +183,44 @@ function extractFirstPath(text: string): string | undefined {
   return text.match(/[\w./-]+\.(ts|tsx|js|jsx|json|md|py|go|rs)/)?.[0];
 }
 
+/**
+ * Quality gate for workspace memory candidates.
+ * Rejects low-quality entries like git hashes, error messages, etc.
+ */
+function shouldAcceptWorkspaceMemoryCandidate(entry: {
+  type: LongTermType;
+  text: string;
+}): boolean {
+  const text = entry.text.trim();
+
+  // Too short
+  if (text.length < 20) return false;
+
+  // Git history / commit hash
+  if (/\b[0-9a-f]{7,40}\b/.test(text)) return false;
+  if (/^(fix|feat|chore|docs|refactor|test):/i.test(text)) return false;
+
+  // Raw error / stack trace
+  if (/^\s*(Error|TypeError|ReferenceError|SyntaxError):/i.test(text)) return false;
+  if (/at \S+ \([^)]+:\d+:\d+\)/.test(text)) return false;
+
+  // Active file list
+  if (/^(modified|created|deleted|renamed)\s+\S+\.\S+$/i.test(text)) return false;
+
+  // Temporary progress
+  if (/^(currently|now|pending|in progress|todo|wip):/i.test(text)) return false;
+
+  // Code signature / API doc
+  if (/^(function|class|interface|type|const|let|var)\s+\w+/.test(text)) return false;
+  if (/^(GET|POST|PUT|DELETE|PATCH)\s+\//.test(text)) return false;
+
+  // Path-heavy facts (rediscoverable from repo)
+  const pathCount = (text.match(/\/[\w.-]+(\/[\w.-]+)+/g) || []).length;
+  if (pathCount > 2) return false;
+
+  return true;
+}
+
 export function parseWorkspaceMemoryCandidates(summary: string): LongTermMemoryEntry[] {
   const match = summary.match(/<workspace_memory_candidates>([\s\S]*?)<\/workspace_memory_candidates>/i);
   if (!match) return [];
@@ -150,6 +234,10 @@ export function parseWorkspaceMemoryCandidates(summary: string): LongTermMemoryE
     const type = item[1].toLowerCase() as LongTermType;
     const body = item[2].trim();
     if (body.length < 12) continue;
+
+    // Apply quality gate
+    if (!shouldAcceptWorkspaceMemoryCandidate({ type, text: body })) continue;
+
     entries.push({
       id: id("mem"),
       type,