Add signed trusted peer path registry

[lukisch]

Summary

• add a host-owned, HMAC-authenticated trusted peer path registry with atomic publish, fail-closed validate, peer-filtered list, and authorized resolve
• add executable pull-plan plus explicit pull --apply for ordinary files over SFTP/Tailscale/LAN with strict known-host verification, an absolute pinned SFTP executable, no inherited SSH config, destination allowlists, local staging, and no-overwrite installation
• add JSON schemas, host-local examples, slot templates, EN/DE documentation, protocol/security/skill/module metadata, and CLI packaging
• enforce the R9 database boundary: SQLite, -wal, and -shm paths are discovery-only with direct_pull=false and adapter=sqlite-transit-sync

Security model

The semi-trusted yard receives exact path metadata, endpoint data, peer IDs, revisions, and signatures only. Referenced file content, credential values, HMAC keys, SSH private keys, known_hosts, validation state, and staging remain host-local. Host/key pins and monotonic revision state reject tampering, replay, and same-revision equivocation; crash-released OS locks serialize publication and revision-pin updates.

HMAC remains deliberately symmetric, so publisher keys must be provisioned only to that publisher's authorized peers. SSH authentication and server-side read-only ACLs remain mandatory external controls. Directory pulls stay blocked pending a reviewed adapter.

Validation

• python -m ruff check .
• python -m pytest -q — 97 passed, 3 local platform/permission skips
• python -m unittest discover -s tests -v — 100 tests, 3 skipped locally
• python -m compileall -q system_gap_master scripts tests
• git diff --cached --check
• python -m build — sdist and wheel built successfully
• installed-wheel smoke: trusted-peer-paths --help exposes publish, validate, list, resolve, pull-plan, and pull