### `wai --version`, `wai docs search` and `wai registry show`, and what a version of the toolchain promises

- **`wai --version`** (`toolchain.show`, also `wai version`), and with `--json` its envelope: this
  binary's version; the catalogue's format, operations and the SHA-256 of `wai/catalogue/ops.json`;
  the envelope's version; the registry's capabilities and the SHA-256 of
  `wai/registry/capabilities.json`; the release of the standard it implements with the envelope
  formats it reads; and the build features the catalogue names that it holds. A test holds the
  crate's version, the export's and the newest release of [CHANGELOG.md](CHANGELOG.md) equal.
- **`wai docs search <word>...`** and **`wai registry show <capability>`**: `docs.search` and
  `registry.show` have a command line now, each the same tool `wai mcp` serves, and a test holds
  each door's answer to the other's. The specification's text is `--spec-root`'s, `$WAI_SPEC_ROOT`'s,
  or the tree the binary was built from; without it `wai docs search` exits 5 (`spec-not-found`), and
  `wai registry show` answers from the registry and says the text is not here. A capability the
  registry does not hold exits 5 (`capability-not-found`). Both now name the feature `mcp`, which
  the release archive's `wai` holds.
- **[VERSIONING.md](VERSIONING.md)** says what is public, what holds each surface in CI, what a
  version number promises and how a change is announced, and states what the catalogue's check does
  not catch: `wai breaking` does not read the catalogue, so an operation removed from it shows in
  the export's diff and fails nothing. **[DEPRECATIONS.md](DEPRECATIONS.md)** lists what is
  deprecated, and a test holds it to the catalogue both ways.
- **A deprecated flag says so when used.** `--confirm` still does what `--yes` does, and now prints
  one line on standard error, `wai: deprecated: --confirm, use --yes instead`. Standard output, the
  envelope and the exit code are as they were.
