fix(harness): align workspace paths and best-practices mount target

- Mount best-practices context at /workspace/best-practices/ (was
  /opt/harness/context/best-practices/) for consistent agent access
- Fix /workspace/working/ → /workspace/project/ in all CLAUDE.md files
  (planning, spec-writing, security-review, code-methodology,
  qwen-code-methodology, test-writing)
- Update best-practices path references in all CLAUDE.md files to
  /workspace/best-practices/

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

harnesses/contexts/best-practices/v1/harness.yaml

@@ -7,4 +7,4 @@ provides: [best-practices]
 
 context_files:
   - source: ./best-practices/
-    target: /opt/harness/context/best-practices/
+    target: /workspace/best-practices/