fix: spec2cli excludes undiscoverable interfaces and validates against Go source

Three codegen fixes:

1. Sub-interfaces (returned by methods on other interfaces but not
   registered with ServiceManager) are excluded from CLI commands.
   Previously generated 1708 top-level commands; most were for
   interfaces that could never be discovered. Now only generates
   commands for interfaces with known service mappings or that are
   directly registered.

2. Unknown types (no Go struct/enum/interface exists) now return
   kindUnsupported instead of kindJSONFallback, preventing generation
   of code referencing undefined types like android.FileDescriptor
   or accessibilityservice.AccessibilityEvent.

3. Out-direction params are passed as zero values instead of requiring
   CLI flags, matching the Go proxy signatures that include out params
   as input parameters.

Additional: validates generated commands against Go source to skip
interfaces/methods whose proxy constructors or method signatures
don't match the specs.

Author: xaionaro@dx.center