P12-T4 Data storage documentation

[SoundBlaster]

Description

Adds docs/data-storage.md — a comprehensive reference for all data storage containers in mcpbridge-wrapper. Covers the SQLite metrics database (SharedMetricsStore), the in-memory collector (MetricsCollector), and the audit log files (AuditLogger), including table schemas, field semantics, data flow, and retention/reset behaviour.

Also adds a "Data Storage" section to docs/architecture.md and its DocC counterpart linking to the new document.

Task: P12-T4 (Phase 12 — Data Collection Enhancements)

Type of Change

• Bug fix
• New feature
• Documentation update
• Refactoring
• CI/CD improvement

Quality Gates

• make test - All tests pass with ≥90% coverage (437 passed, 5 skipped; 96.1% coverage)
• make lint - No linting errors (ruff check src/: all checks passed)
• make format - Code is properly formatted (no source code changed)
• make typecheck - Type checking passes (no source code changed)
• make doccheck - Documentation is synced with DocC (if docs changed)

Documentation Sync

docs/ file	DocC file
docs/architecture.md	Sources/XcodeMCPWrapper/Documentation.docc/Architecture.md

• Documentation changes are synced with DocC catalog (or N/A)

Note: docs/data-storage.md is new and has no existing DocC counterpart; the DocC Architecture.md references it via an external link.

Testing

• Added/updated tests for new functionality (documentation only — no code changes)
• All tests pass locally
• Manually tested the changes (documentation only)

Checklist

• Code follows the project's style guidelines
• Self-review completed
• Comments added for complex code (N/A — documentation only)
• Documentation updated (if needed)
• No new warnings generated
• PR title is descriptive

Validation Report

See SPECS/ARCHIVE/P12-T4_Add_documentation_about_data_storage/P12-T4_Validation_Report.md for full quality gate results.