feat: add Prime Agent harness support

[edwin-zvs]

Summary

• add Prime Agent as the canonical prime-agent harness, with compact prime labels in space-constrained views
• add a first-class adapter crate backed by a flavor-separated Pi-compatible runtime
• support interactive and headless operation, restart resume, reset tracking, private session state, and native forks
• resolve Prime Agent 0.7.0 sessions by authoritative JSONL header ID when the filename UUID differs
• register discovery, doctor guidance, PTY/quiescence capabilities, docs, and a durable harness contract

Verification

• cargo test --workspace
• cargo build
• installed Prime Agent 0.7.0 live probe:
  • interactive session s17eed86dcb3c40e18c8aea5773a6d6e7 reached awaiting-input, accepted typed input, and resumed the same native JSONL after daemon restart
  • headless session sae519ff9c84c467f99055e2d710a6115 reused the same JSONL across turns despite differing filename/header UUIDs and surfaced upstream connection errors
  • native fork sc8208dcc75b64185ad970a615a2b0f72 reached awaiting-input with parentSession pointing to the source JSONL

No recording: this exposes the unchanged upstream Prime Agent TUI; the protocol and persistence probes exercise the Construct-specific behavior.