Multiple agents on same machine overwrite each other's identity

[theflysurfer]

Problem

When two agents run on the same machine simultaneously, wk init writes to a single ~/.walkie/.wk-id file. The second agent's wk init overwrites the first agent's identity, causing:

1. Message misrouting: Messages buffered for agent A are never read because subsequent wk read calls use agent B's identity
2. Silent failure: No error is raised — the agent just never sees its messages

Steps to reproduce

# Terminal 1
wk init agent-alpha
# Terminal 2  
wk init agent-beta
# Terminal 1 — identity has been silently overwritten
wk send "hello"   # Now sends as agent-beta, not agent-alpha
wk read             # Reads agent-beta's queue, misses agent-alpha's messages

Proposed fix

Replace the single ~/.walkie/.wk-id file with per-agent files under ~/.walkie/ids/<agent-name>:

• wk init agent-alpha → writes ~/.walkie/ids/agent-alpha
• wk init agent-beta → writes ~/.walkie/ids/agent-beta (no collision)
• Single agent on machine → auto-detected, no env var needed
• Multiple agents → WK_AGENT=<name> targets the right identity
• wk off removes only that agent's file

Reference implementation: https://github.com/theflysurfer/walkie/tree/feat/per-agent-identity

Environment

• walkie-sh 1.3.0
• Windows 11 + Git Bash (PPID=1 issue makes PID-based approaches unreliable)
• Multiple AI agents (Pi, Claude Code) running concurrently