[FEATURE] Plan Lifecycle Hooks

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

Add hooks for plan lifecycle events to enable tooling integration with Claude Code's planning workflow.

### Requested Hooks

• PlanModeEntered: _Fires when user/Clade Code enters planning mode._
• PlanCreated: _Fires when a new plan is saved._
• PlanModeExited: _Fires when user exits planning mode (assumes plan is accepted and action will be taken)._
• PlanProgress: _Fires when a plan step is marked completed. (optional)_
• PlanCompleted: _Fires when all tasks in a plan are completed._

Enable external tools to respond to planning milestones - complements existing PreToolUse/PostToolUse hooks for execution.

Proposed Solution

Simple hooks that follow the patterns established with PreToolUse/PostToolUse should work reasonably well. The design details should be able to follow the existing hook patterns _(session ID, title, plan status (in progress, approved, updated...), plan file, content, todo list, completed list, etc._

Alternative Solutions

We could monitor the file system for the creation of the plan files, updates to the files, but the details of the progress extraction and other changes are fragile at best.

Priority

Critical - Blocking my work

Feature Category

Developer tools/SDK

Use Case Example

Plans represent development intent - they're valuable artifacts that external systems could act upon:

• Activity tracking - Link plans to branches, PRs, and work items (hooks into status tools outside of AI context windows)
• Notifications - Alert team members when plans are created
• CI/CD triggers - Kick off pipelines when plans are approved
• Analytics - Track planning patterns and effort estimation

Additional Context

_No response_