fix(agent): scope USER.md bootstrap file per agent workspace

[fisherdaddy]

USER.md was always read/written against the main agent workspace and copied to every non-main agent during config sync, so editing "about you" in any agent silently overwrote all others. Bootstrap read/write IPC now accepts an agentId to resolve the correct workspace, config sync no longer propagates USER.md across agents, and the create-agent flow no longer prefills from or writes to the main agent's USER.md.

Summary

Related Issue

Fixes #(issue number)

Changes Made

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Code refactoring
• Documentation update
• Performance improvement
• Other (please describe):

Testing

• Tested locally
• Added new tests
• Updated existing tests
• Manual testing performed

Screenshots (if applicable)

Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

Electron-Specific Changes

• Changes to main process (src/main/)
• Changes to preload script (src/main/preload.ts)
• Changes to IPC communication
• Changes to window management
• None

Additional Notes