spec: V23, use Bitcoin as infrastructure

Promote V23 as the active deployed-infrastructure canon.

Specify and implement Bitcoin-backed audit and spend interfaces without
treating Bitcoin as ENGI's bulk compute or storage layer. Keep ENGI
proof computation and private artifact storage off-chain, add bounded-
public and private commitment scopes, preserve a first-gate sidechain
bridge mode, and fix the naming boundary so ENGI remains the system
while NGI names the share and settlement denomination.

Close first-gate V23 in source with deterministic stubbed-testnet
demonstration service code for audited base-layer purchase carriers,
repeated-read payment carriers, sidechain checkpoint stand-ins, and
anchor publication receipts. Wire the new bitcoin-* artifacts, compute
and storage reality manifests, treasury policy, settlement intent and
observation, and bitcoin proof families through the runtime, API,
browser shell, tests, docs, and generated canon.

Keep the live-boundary posture honest: no live mainnet transaction
broadcast, no live Lightning processor, and no live sidechain operator
are claimed here. V23 now prototype-demonstrates the external
infrastructure contract while preserving explicit deferral of real
network execution.

Stabilize V23 commitment roots by excluding volatile pipeline telemetry
from the private anchor scope, regenerate ENGI_SPEC_V23_PROVEN.md and
the .engi/v23-* promoted reports, and update the embedded walkthrough
copy so the demonstration explains the operator flow clearly from repo
supply through proof, disclosure, and settlement.

Validated with:
- node --test engi-demo/test/core.test.js
- node --test engi-demo/test/api.test.js
- node --test engi-demo/test/workflow.integration.test.js
- node --test engi-demo/test/proven-generator.test.js
- node --test engi-demo/test/e2e.test.js
- node scripts/check-engi-spec-family.mjs --version V23 --mode promoted
- node scripts/check-engi-canonical-inputs.mjs --current-target V23
- node scripts/check-engi-canon-posture-drift.mjs --active-canon V23 --draft-target V24
- node scripts/generate-engi-proven.mjs --version V23 --allow-dirty --check

Author: geraldarthurdavis

ENGI_SPEC.txt

@@ -1 +1 @@
-V22
+V23