V3 Maven CLI toolchain capability pack. By-value connector composition (service_kind=cli, no separate ingredient): one local mvn CLI ingredient exposes bounded project operations for readiness, compile checking, and test execution. Project operations run from an explicit project directory cwd supplied at execution time, use Maven batch mode, suppress transfer progress and snapshot update checks, avoid caller-supplied Maven goals/profiles/properties/settings/toolchains/module selectors, avoid wrapper scripts and shell wrappers, and keep diagnostics visible as text output. Compile and test operations are approval-gated because Maven may resolve dependencies and plugins, execute build plugins, compile project code, run tests, and write target directories or local Maven cache entries. Requires mvn on PATH.