## Why
Resuming a thread can replace saved model settings with global defaults. A selected service tier can also be lost when the current model does not support it.
## What changed
- Restore saved service tier, reasoning summary, and personality on resume unless the caller explicitly overrides them, respecting thread ownership of settings snapshots.
- Retain the selected service tier for persistence, settings notifications, and resume comparisons while filtering the effective tier against the current model's capabilities.
- Carry the runtime model, service tier, and personality into thread revert reconstruction.
- Persist initial thread settings before user input during MCP startup so an interrupted first turn retains its settings checkpoint.
## Testing
Extend regression coverage for cold resume and explicit overrides, unsupported service tiers, settings preservation during revert, and settings checkpoints before user input when MCP startup is interrupted.
GitOrigin-RevId: e5ec012a5678048c5eedd443e524f38c142bf9fd
Eric Traut
430a16799d