feat: blocking permission hook with FIFO-based approval

[hiskudin]

Summary

Replaces the keystroke-injection approach for permission approval (which has been unreliable across all our attempts: AX tree walking, ctrl+backtick, TIOCSTI) with Claude Code's documented hook decision protocol.

When the PermissionRequest hook fires, notify.sh now creates a FIFO at /tmp/stack-nudge-perm-<id>.fifo and blocks reading from it. The notification carries the FIFO path. When the user clicks Allow (banner) or Enter (panel), the app writes allow to the FIFO. The hook reads it, outputs {"hookSpecificOutput": {"hookEventName": "PermissionRequest", "decision": {"behavior": "allow"}}} to stdout, and exits — Claude Code skips its own UI prompt entirely.

Why this works

Claude Code's hook docs explicitly support this pattern:

• Hook can run for up to the configured timeout (we set 600s for PermissionRequest)
• JSON output to stdout drives the decision
• Synchronous semantics — Claude Code waits for the hook before proceeding

This is the proper supported way. No keystroke injection. No AX hacks. No flaky timing.

Changes

• notify.sh — create_perm_fifo() + wait_for_permission_response() use Python select for portable timeout-aware FIFO reads
• install.sh — PermissionRequest hook registered with timeout: 600
• panel/EventStore.swift — NudgeEvent gains fifoPath
• panel/EventListener.swift — decodes fifo_path from socket payload
• panel/Panel.swift — writeFIFO() helper; UNUserNotificationCenter Allow action and panel Enter key both write allow\n to the FIFO, short-circuiting the AppActivator path

Test plan

• Trigger a permission request → Allow button on banner approves it cleanly, no terminal prompt shown
• Same via panel Enter key
• Dismiss the notification → after 550s, hook times out, Claude Code's terminal UI fallback appears
• Stop events (no FIFO) still work via existing AppActivator path
• No orphaned FIFOs in /tmp/ after normal use

🤖 Generated with Claude Code