## Why
Forked subagents can inherit a parent's compacted history, but their context-window metadata needs to identify the child and start a distinct window lineage.
## What changed
- Always identify context windows by agent name and remove the `features.token_budget.mode` setting.
- Persist the agent path in world state and emit context-window metadata as a standalone developer message when the identity changes.
- Reset inherited compaction metadata to the forked subagent's initial context window and restore that window in session state.
## Testing
Extend the full-history subagent test to verify parent and child world-state snapshots, agent identities, distinct window IDs, and the reset child checkpoint.
GitOrigin-RevId: 6584201e57b3d2fba0ce626b89a8b3b0b3c752db
Boyang Niu
69b6152c17