Bug 1: Subagent events from gateway broadcasts were processed as parent
events because the sessionKey filter was accidentally removed during the
subagent decoupling refactor. Re-add the filter in wireChildProcess.
Bug 2: Creating workspaces at custom paths failed because:
- mkdir API rejected absolute paths outside workspace root
- Directory picker started at workspace root, not home
- Error responses from mkdir were silently swallowed
Add absolute path support to mkdir, handle errors in picker UI,
start picker at home dir, and normalize init route paths.
92fadd6700