[Issacboy123]

Summary

Keeps subagents aligned with the parent session when users switch branches or reset context. Active children are stopped safely before the parent context changes, and the subagent list is replaced with the one saved for the destination branch. If Diffex cannot safely stop the children or record a reset, it leaves the existing context in place.

Reasoning

Subagents must be reconciled at the same boundary as parent context changes or children from an abandoned branch can remain active or later reappear. Running extension cancellation and optional summarization first avoids disturbing children for a navigation that will not commit. Quiesce and reset-barrier failures are fail-closed, while cleanup failures after a committed barrier are reported as warnings because the old roster has already been durably masked.

Changes

• Reconciled the controller roster with the newly selected branch after successful tree navigation.
• Quiesced active children immediately before leaf mutation and restored the previous leaf when quiescing or navigation failed.
• Routed reload, manual harness selection, and prompt-boundary harness refresh through one reset path with a durable empty-roster barrier.
• Delayed manual harness selection until the reset boundary succeeds and treated post-barrier cleanup failures as runtime warnings.
• Preserved corrupt-newest snapshot masking and best-effort status writes during navigation.
• Added controller and persistence regressions for navigation ordering, summarization, quiesce failure, reset failure, cleanup failure, and shared harness activation.

Testing

• node ../../node_modules/vitest/dist/cli.js --run test/suite/subagent-persistence.test.ts test/suite/subagent-services.test.ts test/suite/subagent-registration.test.ts test/suite/agent-session-harness-version.test.ts test/session-manager/fork-branch.test.ts test/session-selector-path-delete.test.ts
• npm run check