[KSlashh]

Prevent the operator from sweeping the connector needed to enforce the previous kickoff slot.

• Construct the force-skip connector with the graph's committee N-of-N key. The genesis Pre-Kickoff retains its operator key because it has no preceding graph.
• Add committee nonce slots and SIGHASH_NONE signatures for input 1 of Quick-Challenge and Force-Skip-Kickoff, including digest binding, signature verification and simplified graph serialization.
• Reduce operator pre-signatures from six to four.
• Wait for the previous graph's committee signatures before broadcasting either penalty, and stop once the force-skip connector is settled.

Audit finding: M29.

Requires GOATNetwork/BitVM#23, targeting gc-v2. Cargo currently references that PR's branch; restore gc-v2 and refresh Cargo.lock after the dependency merges.

Nonce and signature message shapes change. Deploy all participating nodes together and recreate existing graphs.

Validation: includes a full operator/committee pre-signing regression checking the connector key, both penalty signatures, rejection of the operator key and simplified graph round-tripping. The zkm notes record passing bitvm-gc/node tests and clippy; these were not rerun during this review.