Refactor and update Persys Compute Platform documentation to reflect current implementation status and roadmap

- Consolidate design specifications into a single document outlining the current state of the compute platform as of 2026-08-04.
- Remove outdated draft specifications and replace with a comprehensive summary of completed phases, including Scheduler HA, Node operations, Vault-managed mTLS, Gateway enhancements, and Workload telemetry.
- Highlight remaining gaps in network abstraction, feature gating, and operational validation.
- Update alignment score to reflect the project's maturity and readiness for production.
- Revise roadmap to focus on stabilization, hardening, and operational excellence rather than new feature development.

Author: miladhzzzz