[Kinflou]

Docs for core#96 4b–4c and core#99. Merge after cli#71: the CLI drift check runs against the cli's default branch, which needs --validate-on-decode.

• guide/idl/validator.md:
  • the "not run" note becomes "run in Rust; TypeScript not yet";
  • value.length (characters, not bytes) and value.name (a path) are defined;
  • @validators goes only on a field or an alias;
  • new On a type alias and In generated code sections (validate() / validate_first(), paths, validate_on_decode).
• guide/idl/types.md: a Type aliases section. Aliases had no guide entry at all.
• reference/congregation/comline-toml.md: the validate_on_decode key, in both tables plus its own section.
• reference/cli.md: --validate-on-decode and its env var.
• design/validators.md: status, 3f, and the phase table brought up to date. A What shipped section replaces the stale "where codegen is today", recording where the implementation departed from the draft (the runtime module instead of comline_rt, path-valued field, a Validate trait, recursion, kernel resolution, the params check).

zensical build --strict passes, as do the CLI drift check (run against the cli#71 binary) and the IDL drift check.