[v0.91.8][runtime-v3][launch] Simplify and harden local Runtime v3 launch path

[danielbaustin]

Objective

Make the Runtime v3 local launch path truthful and reliable using one process
owner and one Rust-native server path.

Scope

• Guardian is the sole process-0 owner for local Runtime v3 launch.
• Production readiness fails closed when required adapters are not configured;
  no degraded executor receives production credit.
• One init file derives scheme, bind address, port, TLS identity, origins, and
  reported readiness endpoint.
• Axum serves the documented Observatory and health routes.
• Continuity identity excludes private-key material.
• Observatory availability distinguishes unimplemented, unavailable, failed,
  and ready states.
• Real authenticated WebSocket exchange and clean-checkout launch proof.

Constraints

• Rust/Tokio/Axum/Rustls only for runtime serving.
• No Python server, shell wrapper, sidecar launcher, fixture credit, plaintext
  secrets, TLS bypass, AWS, or Runtime v2 changes.
• Preserve real functionality; remove duplicate or placeholder launch paths.

Acceptance

1. A clean checkout starts with the documented command and init file.
2. Guardian owns readiness, shutdown, restart, and child reaping.
3. Required production adapters are real or startup fails before readiness.
4. /, /health, /v1/observatory, and /v1/observatory/ws are coherent.
5. Authenticated WebSocket handshake/feed/close is tested against the live
   Axum server.
6. No secret values or private-key hashes enter launch artifacts or continuity
   identity.
7. Focused runtime and launch tests pass; unrelated slow suites stay out of
   the fast launch gate.