fix(prime-agent): preserve final responses

[rynfar]

Prime Agent could complete after tool loops, queued continuations, or reconnects without placing its authoritative final response in the right timeline item. Some completed or failed turns therefore appeared silently blank even though the provider had settled them.

This gives daemon assistant segments unique per-turn identities, keeps reconnect continuations attached to the admitted turn, and classifies authoritative textless terminals in both daemon and ACP paths. The server persists only a provider-neutral outcome, while web and mobile present fixed safe response-status copy without fabricating an assistant message, exposing provider-private details, or changing other providers.

Verification:

• 325 focused tests across 9 server, orchestration, web, and mobile files
• t3, @t3tools/web, @t3tools/mobile, and @t3tools/contracts typechecks
• targeted lint, formatting, and git diff --check
• integrated web and iOS Simulator 26.3 passes for final-response ordering, successful textless completion, and failed textless completion
• iOS evidence used the already-open PR fix(mobile): remove stray composer text #32 guards only to bypass unrelated base-branch idle-thread render errors; those temporary guards were restored and are not part of this PR

Visual evidence SHA-256:

• web response ordering: 1f306df83786e8d61d3ce4a82ad8b29ca410bfa023e5ea0f955accd029c18492
• web successful textless status: f830028e2ec6de6f460854043ba87832374659996342c0ea1ee5c03ecaa811ce
• web failed textless status: b6a7cd6d1ad26e69cc525dd5713a062b0a79722e7deb8b9ba5c8aea1e858be4a
• iOS response ordering: d08c791c59b598e4cf810e24bd37133eed1fc8d9e708aca9b831e451cb78b111
• iOS successful textless status: b51b92f91ff081fee34fd7b6e5a25fbeea39996de72f53ef4fa2f9ed25602b05
• iOS failed textless status: 74e6033588a9684b24e9ebbb30238909023d92e4d7a08d44ea2526324a31bb31

Built with GPT-5.6 Sol in Prime Agent.

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[github-actions]

Thread transfer impact

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