Auto-install hooks during neurostack init

[raphasouthall]

Summary

neurostack hooks install currently requires a separate manual step after neurostack init. Hooks should be set up automatically as part of the init flow.

Proposed Behavior

During neurostack init, after vault setup and config generation:

1. Install systemd harvest timer (existing hooks install logic) — hourly neurostack harvest --sessions 3
2. Detect Claude Code and inject a SessionEnd hook into ~/.claude/settings.json that runs neurostack harvest --sessions 1 on session exit
3. Support other agents (Codex, Gemini) if their hook config paths are detected

UX

• Prompt user during interactive init: "Install automation hooks? (harvest timer + session hooks) [Y/n]"
• --no-hooks flag to skip in non-interactive mode
• Print summary of what was installed

Why

New users don't know about neurostack hooks install and miss out on automatic session harvesting. This is the highest-value automation NeuroStack provides and should be on by default.

Acceptance Criteria

• neurostack init installs harvest timer unless declined
• neurostack init detects Claude Code and adds SessionEnd hook
• neurostack init --no-hooks skips hook setup
• Idempotent — re-running init doesn't duplicate hooks
• neurostack hooks status reflects hooks installed via init