ADR 0067: conditional branch extension reservation

• Scope: B.EQ, B.NE, B.LT, B.GE, B.LTU, B.GEU, B.Z, B.NZ
• Requirement: PTO-ARCH-CONDITIONAL-BRANCH-RESERVATION-001
• Supersedes: only the active-PTO conditional-branch clauses of ADR 0008, ADR 0027, and ADR 0046

Decision

The eight named conditional branch families are not active PTO instructions. Their complete 32-bit encoding forms are occupied extension space. PTO scalar decode rejects every matching form before operand reads or architectural effects, and PTO assembly/disassembly does not expose their spellings.

This reservation does not remove scalar comparison, SETC.*, J, JR, or the block commit-target mechanisms. It changes no encoding outside the eight reserved families.

Rationale

The forms belong to the two-level block-body architecture. Keeping them in the active PTO scalar catalog would contradict that ownership boundary and allow a PTO implementation to consume extension encodings that must remain collision-protected.