v0.8.69: define CLI/TUI parity for subagent and runtime control surfaces

[Hmbown]

Context

During v0.8.67 RC hardening, the TUI sidebar became the primary interactive place for subagent status, expand/collapse, and cancellation. That is the right product shape for the terminal, but the same control surfaces should not be trapped inside the TUI if we want a future cloud app, remote workbench, or headless CLI to drive CodeWhale consistently.

Goal

Define and implement a parity contract where user-visible TUI actions have a CLI/control-plane equivalent when it is reasonable and safe.

Initial scope

• Subagents: list/status/inspect, cancel, and lifecycle state should be available through a non-TUI command path as well as the sidebar.
• Jobs/runtime: cancellation and status affordances should have stable command/API equivalents rather than only mouse/UI affordances.
• Providers/setup: provider routing and setup report actions should expose a scriptable path where practical.
• Docs/help: help text should make clear when a TUI affordance has a CLI/headless equivalent.

Acceptance sketch

• A small command/control-plane matrix maps core TUI affordances to CLI/API equivalents or explicitly documents why not.
• Subagent cancel/status can be exercised without opening the TUI.
• Tests cover at least one TUI path and one non-TUI path for subagent lifecycle control.

Filed from the v0.8.67 RC-hardening pass so the release patch can keep moving without burying this product direction.