v2.3.0 added ajv to the install layout but forgot ajv's transitive deps
(fast-deep-equal, fast-uri, json-schema-traverse, require-from-string).
require('ajv') succeeded but new Ajv() crashed on first use, breaking
every plugin-input-schema validation under the v2.3.0 plugin loader.

- bin/install.js: walk ajv/package.json#dependencies and copy each
- bin/install.js: post-install probe forks plugin-input-schema-validator
  end-to-end so future ajv-dep drift fails loudly at install time
- tests/install/ajv-transitive-deps.test.js: regression test
- CHANGELOG, version bumps in package.json and .claude-plugin/plugin.json