updateDraft preserved summarizedFor whenever the plan text was
unchanged, but the modal re-syncs the draft on model selection
changes too. Result: blur under model A, switch to model B without
editing text, click Start, and the running session kept model A's
title. The skip condition in startExistingSession only checks
text equality, not model identity.
Now updateDraft preserves summarizedFor only when both the plan
text AND the persisted modelProvider/modelId are unchanged, so a
model switch implicitly invalidates the marker and the start path
re-summarizes under whatever model the user just picked.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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