[FEATURE] Add YAML frontmatter with metadata to auto-generated plan files

Problem Statement

When Claude Code creates plan files in ~/.claude/plans/*.md, they contain only the plan content without any metadata. As far as I can see it, the Markdown file names are random, e.g. indexed-brewing-teapot.md.

This makes it difficult to:

• Track when plans were created
• Correlate plans with specific Claude sessions
• Understand the context in which a plan was generated

Proposed Solution

Include a YAML frontmatter block at the top of auto-generated plan files with metadata such as:

---
created: 2025-01-15T14:30:00Z
session_id: abc123xyz
model: claude-sonnet-4-5-20250929
working_directory: /path/to/project
---

Potential fields to include:

• created - ISO 8601 timestamp of when the plan was generated
• session_id - The Claude Code session identifier
• model - The model used during planning
• working_directory - The directory context when the plan was created
• git_branch - Current git branch (if in a repo)
• plan_name - The auto-generated plan name (e.g., "iterative-booping-parnas")

Alternative Solutions

• Adding a separate metadata JSON file alongside each plan
• Storing metadata in a central index file
• Embedding metadata as HTML comments instead of YAML frontmatter

YAML frontmatter is preferred because it's a well-established convention (used by Jekyll, Hugo, Obsidian, etc.) and is easily parseable.

Priority

Medium - Would be very helpful

Feature Category

Configuration and settings

Use Case Example

1. User generates multiple plans over several days
2. Later, user wants to find a plan from a specific session or time period
3. With frontmatter metadata, they can easily grep or search for plans by date/session
4. This enables better organization and retrieval of planning history

Additional Context

This would be especially useful for users who:

• Work on multiple projects and generate many plans
• Want to audit their planning history
• Build tooling around Claude Code's plan files
• Use tools like Obsidian that can leverage YAML frontmatter for organization