fix(workhub): admit coordination actions through Runtime turns

[ARE404]

Summary

WorkHub actions previously bypassed root Turn admission, and clarification/resume could write synthetic assistant summaries. Admit Host actions into real Coordination Turns/Runs, persist typed Runtime receipts, and materialize/recover them through the shared transcript. Target Sessions retain assignment, Stop and resume authority; no extra model answer is invoked to create a Turn.

Completed requests replay their original acknowledgement without repeating effects. Interrupted attempts close through Runtime recovery; retries receive a new Turn. Clarification after a refused action has its own Turn. Intent, Resolver and clarification model calls remain future work inside this execution boundary.

Refs #3492. Independent follow-up to #4924.

Verification

• The production admission assertion failed before the change. Production tests now cover real Run/terminal facts, zero Coordination model calls, shared-transcript receipts, replay, restart, Stop/Resume and refused-resume clarification.
• Full Core, Storage, Runtime and Desktop suites passed (821 / 1198 / 3316 / 2392 tests). Final admission/projection changes also passed 85 WorkHub, 74 Runtime repair/read-model and 38 Desktop flow/projection tests.
• Host full rerun: 1788 passed, 12 skipped, one launcher process-exit timeout. That test and the Node/Electron process-exit timeout from the earlier run each passed isolated reruns. A fully green Host aggregate is still needed from CI.
• Build, typecheck, lint, format, renderer architecture, Astryx inventory, ASF headers, protocol epoch guard and Desktop/UI knip checks passed.
• Storybook receipt fixture rendered in light/dark without page errors. These are component fixtures; runtime delivery is covered separately by the production tests above.

Dark appearance

Compatibility and review focus

Compatibility epoch moves from 125 to 126: the synthetic workhub.coordination.record operation is removed and typed receipts extend transcript decoding. Released summaries remain readable. Transactional delegation/Stop linkage facts remain in their existing authority; receipts acknowledge operations rather than mirror target execution state.

• Green CI for the current head, including the complete Host suite.

AI use

• No generative tool made a substantive contribution
• Generative tooling made a substantive contribution

Tool(s) and scope: Codex implemented the repair, tests, documentation and component evidence.

Checklist

• Tests cover the change and fail without it
• Lint, format, typecheck and the affected suites pass locally — static checks pass; Host aggregate timeouts are disclosed above.

Does this PR entail a change in behavior?

• Yes — described under Summary above
• No