refactor: split CLAUDE.md into focused documentation structure

- Restructure docs into topic-specific files to minimize context
- Create docs/workflow.md (Git + Agent workflow)
- Create docs/commands.md (Common failures + build commands)
- Create docs/architecture.md (System design + data flow)
- Create docs/testing.md (Test structure + guidelines)
- Rewrite CLAUDE.md as concise hub with links to detailed docs
- Update .gitignore to exclude data/ directory

Benefits:
- Reduced context size for AI assistants
- Faster reference lookups
- Better maintainability
- Topic-focused documentation

Closes #13

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

docs/workflow.md

@@ -0,0 +1,75 @@
+# Development Workflow
+
+## Git Workflow Policy
+
+**CRITICAL: All code changes MUST follow this workflow. Direct pushes to `main` are ABSOLUTELY PROHIBITED.**
+
+1. **Create Gitea Issue First** — All features, bug fixes, and policy changes require a Gitea issue before any code is written
+2. **Create Feature Branch** — Branch from `main` using format `feature/issue-{N}-{short-description}`
+3. **Implement Changes** — Write code, tests, and documentation on the feature branch
+4. **Create Pull Request** — Submit PR to `main` branch referencing the issue number
+5. **Review & Merge** — After approval, merge via PR (squash or merge commit)
+
+**Never commit directly to `main`.** This policy applies to all changes, no exceptions.
+
+## Agent Workflow
+
+**Modern AI development leverages specialized agents for concurrent, efficient task execution.**
+
+### Parallel Execution Strategy
+
+Use **git worktree** or **subagents** (via the Task tool) to handle multiple requirements simultaneously:
+
+- Each task runs in independent context
+- Parallel branches for concurrent features
+- Isolated test environments prevent interference
+- Faster iteration with distributed workload
+
+### Specialized Agent Roles
+
+Deploy task-specific agents as needed instead of handling everything in the main conversation:
+
+- **Conversational Agent** (main) — Interface with user, coordinate other agents
+- **Ticket Management Agent** — Create/update Gitea issues, track task status
+- **Design Agent** — Architectural planning, RFC documents, API design
+- **Code Writing Agent** — Implementation following specs
+- **Testing Agent** — Write tests, verify coverage, run test suites
+- **Documentation Agent** — Update docs, docstrings, CLAUDE.md, README
+- **Review Agent** — Code review, lint checks, security audits
+- **Custom Agents** — Created dynamically for specialized tasks (performance analysis, migration scripts, etc.)
+
+### When to Use Agents
+
+**Prefer spawning specialized agents for:**
+
+1. Complex multi-file changes requiring exploration
+2. Tasks with clear, isolated scope (e.g., "write tests for module X")
+3. Parallel work streams (feature A + bugfix B simultaneously)
+4. Long-running analysis (codebase search, dependency audit)
+5. Tasks requiring different contexts (multiple git worktrees)
+
+**Use the main conversation for:**
+
+1. User interaction and clarification
+2. Quick single-file edits
+3. Coordinating agent work
+4. High-level decision making
+
+### Implementation
+
+```python
+# Example: Spawn parallel test and documentation agents
+task_tool(
+    subagent_type="general-purpose",
+    prompt="Write comprehensive tests for src/markets/schedule.py",
+    description="Write schedule tests"
+)
+
+task_tool(
+    subagent_type="general-purpose",
+    prompt="Update README.md with global market feature documentation",
+    description="Update README"
+)
+```
+
+Use `run_in_background=True` for independent tasks that don't block subsequent work.