refactor: restructure workspace file organization (#121) (#122)

## Path Changes
- audit.log: memory/audit.log → log/audit.log
- projects.json: memory/projects.json → projects/projects.json
- prompts: roles/<project>/<role>.md → projects/prompts/<project>/<role>.md

## Files Updated
- lib/audit.ts - new audit log path
- lib/projects.ts - new projects.json path
- lib/dispatch.ts - new prompt instructions path
- lib/tools/project-register.ts - prompt scaffolding path
- lib/setup/workspace.ts - workspace scaffolding paths
- lib/context-guard.ts - projects.json path
- lib/tools/setup.ts - tool description
- lib/templates.ts - AGENTS.md template path references

## Documentation Updated
- README.md
- docs/ARCHITECTURE.md
- docs/ONBOARDING.md
- docs/QA_WORKFLOW.md
- docs/ROADMAP.md
- docs/TESTING.md

Addresses issue #121

docs/ROADMAP.md

@@ -35,7 +35,7 @@ The pipeline definition replaces the hardcoded `Doing → To Test → Testing
 ### Open questions
 
 - How do custom labels map? Generate from role names, or let users define?
-- Should roles have their own instruction files (`roles/<project>/<role>.md`) — yes, this already works
+- Should roles have their own instruction files (`projects/prompts/<project>/<role>.md`) — yes, this already works
 - How to handle parallel roles (e.g. frontend + backend DEV in parallel before QA)?
 
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