idle-done accepts any non-read-only command exiting 0 as verification

Deferred from the v0.10.0 release review. Self-disclosed; gated to run mode, so interactive users are unaffected.

With no configured verify command, `packages/opencode/src/cli/cmd/idle-done.ts:157` treats **any** non-read-only bash command exiting 0 as evidence that verification passed.

An unrelated mutating command — an install, a build script, a cleanup — therefore satisfies the completion signal without verifying anything about the actual task.