Treat fast mode as opt-in

[BinSquare]

pi-harness reads turn.fastMode !== false, so a turn that never mentions fastMode runs in fast mode on any fast-capable model. Only the web UI ever sets the field, so every other entry point — CLI, API clients, integrations — leaves it undefined and silently opts in.

Two things make this look unintended rather than deliberate:

• claude-harness.ts:475 reads the same field as turn.fastMode && …, i.e. opt-in. The two harnesses disagree on the default for one TurnOptions field, so switching harness silently changes which tier a turn bills against.
• core/turn-options.ts sets NON_INTERACTIVE_FAST_MODE = false for triggered turns and omits the field otherwise — deliberately keeping turns off fast mode, which pi-harness then reads as "on".

This is generated by QM.

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