[P2.1-T05] Implement mode-based action execution

[RichardHightower]

Task: Implement mode-based action execution

Phase: 2.1 - Core Governance
Estimated: 1 day
File: cch_cli/src/hooks/actions.rs
Depends on: P2.1-T03

Description

Update action execution to respect rule mode (enforce/warn/audit).

Acceptance Criteria

• Update execute_action to check rule mode
• Enforce: Current behavior (block/inject/run)
• Warn: Never block, inject warning message instead
• Audit: Skip action, log only
• Create warning context injection for warn mode
• Add integration tests for each mode

Mode Behavior Matrix

Mode	Blocks?	Injects?	Logs?
enforce	Yes	Yes	Yes
warn	No	Warning only	Yes
audit	No	No	Yes

Code Reference

fn execute_action(rule: &Rule, action: &Action, event: &Event) -> ActionResult {
    let mode = rule.mode.unwrap_or_default();
    
    match mode {
        PolicyMode::Enforce => execute_action_impl(action, event),
        PolicyMode::Warn => {
            if action.is_block() {
                ActionResult::Warning(format!("Rule '{}' would block: {}", rule.name, action.reason()))
            } else {
                execute_action_impl(action, event)
            }
        }
        PolicyMode::Audit => ActionResult::Audited,
    }
}

[RichardHightower]

Completed in PR #72