feat: add GSD Memory cross-project knowledge system

Implements MCP server for semantic search across GSD projects:

MCP Tools:
- gsd_memory_search: Search across all registered projects
- gsd_memory_decisions: Find decisions from SUMMARY/PROJECT.md
- gsd_memory_patterns: Find patterns from SUMMARY.md
- gsd_memory_pitfalls: Find pitfalls from RESEARCH.md
- gsd_memory_stack: Find tech stack entries
- gsd_memory_register: Register project with memory
- gsd_memory_index: Trigger indexing/update
- gsd_memory_status: Show system status

Architecture:
- QMD wrapper with grep fallback when QMD unavailable
- YAML frontmatter extractors for GSD document types
- Project registry at ~/.gsd/projects.json
- Auto-install via bin/install.js for Claude Code

Workflow integrations:
- new-project: Registers project with memory
- plan-phase: Indexes after planning
- execute-phase: Indexes after execution
- complete-milestone: Indexes milestone completion
- Researcher agents query memory before Context7

Tests: 117 passing (66 unit + 51 integration)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

gsd-memory/dist/tools/stack.d.ts

@@ -0,0 +1,19 @@
+export interface StackResult {
+    library: string;
+    version?: string;
+    purpose?: string;
+    project: string;
+    phase?: string;
+    source: string;
+    sourceType: 'summary' | 'research';
+}
+export interface StackOptions {
+    query?: string;
+    project?: string;
+    limit?: number;
+}
+/**
+ * Search for tech stack entries across all registered GSD projects
+ */
+export declare function findStack(options: StackOptions): Promise<StackResult[]>;
+//# sourceMappingURL=stack.d.ts.map