feat: add session management and execution verification

[ajaygunalan]

Summary

• Add /pause command to save session state before ending work
• Add /resume command to restore context at session start
• Add /verify-execution command to check if execution matched the spec
• Update project-install.sh to create STATE.md on install

Details

Session management enables context continuity across Claude sessions:

• STATE.md tracks active spec, progress, and next steps
• /pause auto-detects active spec from most recent folder in specs/
• /resume reads STATE.md and displays context for quick orientation
• /verify-execution compares git changes against spec scope

Test plan

• Run /shape-spec to create a spec
• Execute tasks in plan mode
• Run /pause and verify STATE.md is updated
• Start new session, run /resume and verify context is shown
• Run /verify-execution and verify it detects changed files

🤖 Generated with Claude Code