feat(orchestrator): new_task thinking_effort — subtask start effort, switchable before entering (DTE series 5/5)

[easonLiangWorldedtech]

What

Orchestrator support: new_task accepts an optional thinking_effort, the user can change it in the new-task ask block before clicking Enter, and the value becomes the child task's initial effective effort (shown on the child's header chip at init).

Part of the Dynamic Thinking Effort series (5 PRs). Master design issue: easonLiangWorldedtech#28.

PR protocol (all series PRs): draft PR until CI is fully green -> switch to ready -> CodeRabbit bot review addressed in full -> 100% test coverage on patch lines. Each PR <= 1000 diff lines, based on latest upstream main (stacked on preceding series PRs where noted; rebased to pure main once dependencies merge).

Stacking: PR 5/5 — stacked on PR 2 (task state).

Design

• new_task tool schema: optional thinking_effort (validated against the child model's capability array)
• Ask block: effort selector pre-filled with the model-specified value, or the parent's current effective effort when unspecified; editable before Enter
• delegateParentAndOpenChild receives thinkingEffort? and applies it at child task init

Acceptance criteria

• Model can specify a subtask start effort; unspecified => parent's current effective effort pre-fill
• User can switch before Enter; the child task initializes with the chosen value (child chip init state correct)
• Tests: schema param validation, ask pass-through, child init; 100% patch coverage; <= 1000 diff lines