Prevent follow-up cards from interrupting Freebuff base2 runs

[peter-research]

Summary

• Disable suggest_followups by default for Freebuff's base2 roots, matching the existing Fable variant's behavior.
• Keep ask_user available so agents can still ask necessary clarifying questions.
• Preserve follow-up cards for Codebuff modes and allow Freebuff variants to opt back in explicitly with noFollowups: false.
• Add tests for defaults and the explicit override.

This addresses the failure mode described in #1434: time-limited Freebuff runs can stop on optional follow-up cards even when the user asked the agent to continue working.

Testing

Added regression coverage in agents/__tests__/base2.test.ts. I haven't run the Bun test suite in this environment.

[codebuff-team]

Nice, tightly scoped fix. The change in agents/base2/base2.ts only flips the default for noFollowups when mode === 'free', which matches the stated goal of aligning Freebuff's base2 root with the existing Fable variant's behavior, and it's a one-line functional diff with a clear comment explaining the rationale (tied to #1434).

The tests in base2.test.ts cover both directions: default suppression for free mode while keeping ask_user, and the explicit noFollowups: false opt-in, plus a check that default/lite/max are unaffected. That's the right test shape for this kind of default-flip change.

A couple of things worth double-checking before porting:

• Confirm that mode === 'free' is actually synonymous with "Freebuff base2 root" everywhere it's called, and that no other caller relies on free mode still emitting follow-up cards by default (e.g. any UI/CLI flow that expects the card even in free mode for non-Freebuff use). A grep for createBase2('free' call sites would be good due diligence.
• The PR description says you haven't run the Bun test suite - please do before merge, just to catch any snapshot or fixture that encodes the old default.

Overall this looks like a correct, minimal, well-reasoned fix with matching tests. Happy to see this ported pending the default-overlap check above.