refactor(peer): separate reachability from Mesh ownership

[M4n5ter]

Summary

• introduce one bounded, self-signed reachability lease as the identity-bound locator contract, independent of Peer Mesh membership
• publish that lease through authenticated Host status and consume it consistently from owner connection codes, Guest mounts, Desktop profiles, and CLI projections
• reject unsigned direct route arrays at the unpublished persistence and protocol boundaries, moving the compatibility boundary to epoch 98
• record the frozen four-layer recovery design, invariants, and acceptance criteria used by this stack

Refs #4554

Verification

Verified on the complete stacked head after rebasing from main at eacfb46aa7ec93273bf468335f4270bba62d35a5:

• npm run typecheck
• npm run lint
• npm run format:check
• npm run rebuild
• npm run test:dist - all workspace tests passed
• npm run check:renderer-architecture - 71 passed
• npm run check:release - 192 passed
• git diff --check
• cargo fmt --manifest-path native/runtime-host-peer/Cargo.toml -- --check
• cargo clippy --locked --all-targets --manifest-path native/runtime-host-peer/Cargo.toml -- -D warnings
• cargo test --locked --manifest-path native/runtime-host-peer/Cargo.toml - 28 passed
• immutable installed-CLI tarball smoke

Review focus

The lease proves who issued a bounded locator snapshot; it does not grant membership or access. Consumers still authenticate the Runtime Host and require the expected PeerId before retaining or using the lease.

AI use

• No generative tool made a substantive contribution
• Generative tooling made a substantive contribution

Tool(s) and scope: Codex implemented and verified the change under maintainer direction.

Checklist

• Tests cover the change and fail without it
• Lint, format, typecheck and the affected suites pass locally

Does this PR entail a change in behavior?

• Yes - described under Summary above
• No

[jackwener]

Approved at exact head e86dc0bc8194e0dc5d1bab6a2aa26e603b19162f at the explicit direction of M4n5ter. No technical review was performed as part of this action; M4n5ter requested the approval and accepts responsibility for subsequent handling.

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Review notice: This approval was submitted by an automated review agent operated by WAWQAQ and is published at the direction of M4n5ter, who requested this action and is the human accountable for it.