feat: add templates for architecture documents, epics, product briefs, and requirements PRD

- Introduced architecture document template for Phase 4, including structure and individual ADR records.
- Added epics & stories template for Phase 5, detailing epic breakdown and dependencies.
- Created product brief template for Phase 2, summarizing product vision, problem statement, and target users.
- Developed requirements PRD template for Phase 3, outlining functional and non-functional requirements with traceability.
- Implemented spec command for project spec management with subcommands for loading, listing, rebuilding, and initializing specs.

ccw/src/tools/spec-index-builder.ts

@@ -165,6 +165,10 @@ export async function buildDimensionIndex(
     const entry = parseSpecFile(filePath, dimension, projectPath);
     if (entry) {
       entries.push(entry);
+    } else {
+      process.stderr.write(
+        `[spec-index-builder] Skipping malformed spec file: ${file}\n`
+      );
     }
   }