Issue cause

• The roc build executable is running through the portable serialized ModuleEnv path. That path drops the module identity the interpreter needs for method dispatch.

• roc build writes a portable serialized blob (SERIALIZED_FORMAT_MAGIC)
  (src/cli/main.zig:2670). The built executable loads it via
  setupModuleEnvFromSerialized
  (src/interpreter_shim/main.zig:396, src/interpreter_shim/main.zig:629).

• During portable deserialization,
  ModuleEnv.Serialized.deserialize sets module_name_idx to Ident.Idx.NONE
  (src/canonicalize/ModuleEnv.zig:2054), even though the serialized struct
  reserves space for “interned during deserialization”
  (src/canonicalize/ModuleEnv.zig:1962).

• At runtime, nominal types translate their origin_module into the
  interpreter’s runtime_layout_store.env ident space by string-inserting
  the module name (src/eval/interpreter.zig:8938–8941). As a result, Animal
  ends up with an origin_module ident representing the app module’s name.

• When evaluating dog == cat, the interpreter tries to resolve the is_eq
  method via resolveMethodFunction. This starts by mapping
  origin_module → ModuleEnv using getModuleEnvForOrigin
  (src/eval/interpreter.zig:7734). In the build/shim case, the app module is
  not in imports, so the only intended match is the “app module” check
  (src/eval/interpreter.zig:7755–7761) or translated_module_envs.

• However, Interpreter.initWithModuleEnvs skips populating
  translated_app_module and translated_module_envs for any env whose
  module_name_idx is NONE (src/eval/interpreter.zig:536–603).

  Result: getModuleEnvForOrigin returns null for the app module, and
  resolveMethodFunction fails with MethodLookupFailed.

• Why it only happens with build:

• The built executable uses the portable deserialization path described
  above.

• ./zig-out/bin/roc ./file.roc goes through a path where module envs retain
  a valid module_name_idx. The origin-module → env mapping works, and the
  failure is avoided.

Fix

Insert valid module_name_idx values in interpreter_shim/main.zig after enableRuntimeInserts makes the interners writable, but before Interpreter.init is called.