weave

Transition state from SeamState.Weaving to SeamState.Woven. Re-asserting SeamState.Woven on an already-woven seam is a harmless no-op.

Refused once SeamState.Torn, throwing IllegalStateException: Torn is terminal on every real seam — the invariant SeamStateGate exists to make unrepresentable — so a fake that can be un-torn lets a test construct an input no conforming seam can present. That is the same permissive-fake shape as the constructor guards above (#2432/#2536), one arm over: they close the entry into a state production cannot reach, this closes the exit from one it can.

Why this is loud where tear is a silent no-op. The two arms differ deliberately, and the asymmetry is the contract's, not an oversight. tear() after tear() asks for the state the seam is already in, and Seam.close is idempotent on every real seam (SeamStateGate.tear returns false rather than throwing) — so silence there is the contract. weave() after tear() asks for a transition no seam performs, and has no idempotent reading: the caller believes something false about the seam it holds. Silently ignoring it would leave that belief in place and the assertions built on it green. deliver is the established precedent — also a test-driver helper, also refusing loudly on a torn seam, for the same reason.

Note this is reachable only from a test holding a concrete FakeSeam: weave is not on Seam, so a component under test can never drive it (#2622).