Remote open: carry record length and production index metadata

[bedipritpal]

Stage 4: capability-gated open metadata on upstream8a5812af after PR188.

• New clients advertise capability0x200; supporting servers carry immutable record length and successful production-index bindings in OpenTableAck TLVs. Legacy clients keep the existing reply; missing/rejected metadata retains wire fallback.
• Existing OpenIndex handler/parser, rollback, session-local bindings, natural-order setup, output capacity checks and hardening remain. No separate GetRecordLength/OpenIndex request for a valid warmed production bag.
• Warm bindings are consumed only for the matching production-bag stem; confirmed bag identity is installed before initial auto-open. Existing CDX/Z01 stem convention retained.

Nine files (+212/-7). No count-cache policy/OPENADS_FRESH_COUNTS, daemon-hardening exemptions, Harbour RDD core, lock, no-link jail, health backend or CI/workflow changes.

Credit: scoped work derives from Pritpal Bedi's released mtfix41 source. Two deliberate guards above differ from that source; no whole-function identity claim. This is an RTT saving, not a fresh elapsed startup/CPU or Vouch benchmark.

Fresh Linux GCC11 Debug normal/TLS builds on the actual PR188 merge: selected30cases/1,387assertions each, passed. Covers CDX/Z01, initial natural row, same-bag dedup, independent logins, parked reopen, legacy capability gate, short mandatory payloads, scoped navigation, exclusive behavior and stage3 positions. Known flaky teardown excluded; warnings-as-errors OFF. Earlier overbroad suites timed out in slow CDX reindex and unrelated DD-view tests without assertion failures; not claimed as passing. No full CTest, fresh hosted cross-platform/Vouch validation, exhaustive optional-section fuzzing or full old-server binary interop claimed.