v2.0 — Wire the Critic node

[Ekam-Bitt]

The Critic sits between coder and reviewer and asks what the coder could not see from inside the work: which assumptions are load-bearing, which files were never read, whether a materially different fix is better, what else could break.

Already present: CriticOutput in contracts.py and prompts/critic.md. Wiring it is one graph edge — the seam was built in Phase 1A specifically so adding it would not be a schema migration.

Why deferred: introducing a second reasoning node before the repair loop is reliable means debugging two new failure modes at once. The repair loop has now fired live exactly once (the first click solve needed two attempts), which is not enough evidence that it is reliable.

Measure it as a rung: Stages in graph/router.py gates stages for ablation, so the Critic should be added there and evaluated the same way — does it raise solve rate enough to justify another model call per attempt?