T7: Add config DSL methods (redact, redact_group, redact_pattern)

[dpaluy]

Task Details

Priority: p1 | Story Points: 3 | Group: B (Core Infrastructure)
Depends on: T3

Files

• lib/tracebook/config.rb
• test/lib/config_test.rb

Acceptance Criteria

• config.redact :email, :phone enables patterns
• redact_group :api_keys works
• redact_pattern(/x/, "[X]") works
• Invalid symbol raises ConfigurationError at config time

Context

Part of PII Redaction Architecture Refactor - Phase 2: Pattern System

See full plan: docs/plans/260106-02b-pii-redaction-architecture.md