[P2.2-T02] Extend LogEntry struct with governance fields

[RichardHightower]

Task: Extend LogEntry struct with governance fields

Phase: 2.2 - Enhanced Logging
Estimated: 0.25 day
File: cch_cli/src/logging/mod.rs
Depends on: P2.2-T01

Description

Add new governance fields to LogEntry for enhanced auditability.

Acceptance Criteria

• Add mode: Option<PolicyMode> field
• Add priority: Option<i32> field
• Add decision: Option<Decision> field
• Add metadata: Option<RuleMetadata> field
• Use #[serde(skip_serializing_if = "Option::is_none")] for all new fields
• Verify existing log parsing still works

Example Log Entry

{
  "timestamp": "2025-01-21T14:32:11Z",
  "session_id": "abc123",
  "event": "PreToolUse",
  "rule_name": "no-console-log",
  "mode": "enforce",
  "priority": 100,
  "decision": "blocked",
  "metadata": {
    "author": "cch-skill",
    "created_by": "react-skill@2.1.0"
  }
}

[RichardHightower]

Completed in PR #72