Add KB setup contracts and Percolation V2

[0thernet]

Ships the reviewed KB lifecycle slice as 0.19.0.

• adds deterministic KB customization preparation with filesystem-only scaffolding and explicit runtime preparation reporting
• adds authored typed-relationship commands and strict graph validation without inferred edges
• adds versioned Percolation V2 while preserving byte-stable V1 parsing, ordering, and duplicate behavior
• adds packed companion-skill guidance and updates public docs and package identity
• hardens Unicode target identity, dense concept-ID allocation, package smoke, and exact skill inventory checks

Local proof on the exact branch: canonical check passed with 1,227 tests, 12,479 assertions, TypeScript, build, package smoke, and the Rust URL metadata helper. The prepared package contains 204 files and 4,980,722 unpacked bytes.