fix(core): ordered, idempotent durable tool decisions (follow-ups to #1828)

[EmersonBraun]

Follow-ups from the final review of #1828 (durable tool decisions):

1. Ordered resume: `decide` persists the decision without resuming the model unless the target call is in the last assistant message and nothing else awaits confirmation. With multiple calls, resume happens once all are decided, with results placed right after the assistant message that made them. This keeps strict providers happy.
2. Idempotent decisions: pending calls are registered on arrival. A repeated identical `approve`/`deny` (e.g. double click, or before the stream ends) is a no-op. Only a conflicting decision errors.
3. Denied decisions don't stop the stream: the re-check runs before `stop()` in `prepare`.

Documented limit (no store contract change): rebuilding a multi-call streamed turn after a restart requires `ChatMemory`. Without it, recovery fails with a typed error instead of resuming with an incomplete history. A live controller is not affected.

Checks run locally:

• 569 core tests;
• all 52 quality gates;
• pre-push (lint/build), regenerated docs index;
• `pnpm size` within budget.

A changeset (patch) is included.

🤖 Generated with Claude Code

[github-actions]

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