Add control-plane direct shell commands

[roackb2]

Summary

• add a core chat direct-shell service for shared !command semantics over shell-process policy
• expose controlPlane.sessionDirectShellAsync and route cli-v2/web-v2 through it
• add direct-shell live activities, shared prompt parsing, and regression coverage

Validation

• yarn typecheck
• yarn test src/tests/unit/client-shared/prompt-input-service.test.ts src/tests/unit/client-shared/session-activity-service.test.ts src/tests/unit/cli-v2/control-plane-session-store.test.ts src/tests/integration/control-plane/session-lifecycle.test.ts
• yarn build

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Drain queued prompts after direct shell runs

When a direct shell run is accepted while the session already has queued prompts (for example, a user sends !cmd after a turn finishes but before the queued-drain starts, or any session has queued prompts with no in-flight run), this run never restarts the queue after it settles. buildSubmitPromptRun wires onSettled to startNextQueuedPrompt, but this direct-shell run object only defines execute/onError, so the queued prompts can remain stuck until another normal prompt submission happens to trigger the drain.

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