feat(loop): complete Issue #5 Phase 4 immutable runtime and freeze removal

- Implement eager module loading (lib_py.loop.eager) to preload all framework
  dependencies into sys.modules and enforce PYTHONDONTWRITEBYTECODE=1.
- Synchronize runtime protocol version with MAM_VERSION constant (4.3.0).
- Bypass /tmp/mam-loop-freeze.XXXXXX copy overhead by default in Python mode
  while preserving legacy rollback fallback (MAM_LOOP_PY=0 / MAM_LOOP_FREEZE=1).
- Add tests/test_issue5_phase4_runtime.py verifying eager import completeness,
  mid-flight code modification immunity (B-13), and freeze bypass.
- Pass full test suite (749 tests, 0 failures).

.agents/skills/lib_py/loop/eager.py

@@ -0,0 +1,124 @@
+"""Eager module loading for immutable runtime immunity (Issue #5 Phase 4).
+
+Ensures all dependencies (loop, delegation, agents, external packages)
+are loaded into sys.modules at loop startup, preventing mid-flight disk
+modifications from triggering lazy-import syntax/EOF errors (B-13).
+"""
+
+from __future__ import annotations
+
+import importlib
+import os
+import sys
+from typing import List, Sequence
+
+# Framework version locked with framework constants
+FRAMEWORK_VERSION = "4.3.0"
+
+CORE_MODULES: Sequence[str] = (
+    # Standard library modules
+    "atexit",
+    "argparse",
+    "copy",
+    "glob",
+    "hashlib",
+    "json",
+    "os",
+    "pathlib",
+    "re",
+    "shutil",
+    "signal",
+    "sqlite3",
+    "subprocess",
+    "sys",
+    "tempfile",
+    "time",
+    "typing",
+    # Framework loop modules
+    "lib_py.loop.parser",
+    "lib_py.loop.checkpoint",
+    "lib_py.loop.runner",
+    "lib_py.loop.attribution",
+    "lib_py.loop.autocomplete",
+    "lib_py.loop.evidence",
+    "lib_py.loop.policy",
+    "lib_py.loop.shadow",
+    "lib_py.loop.store",
+    "lib_py.loop.watcher",
+    # Delegation and common modules
+    "lib_py.paths",
+    "lib_py.state",
+    "lib_py.atomic_yaml",
+    "lib_py.workspace_uuid",
+    "lib_py.verify_session",
+    "lib_py.layout",
+    "lib_py.delegation.engine",
+    "lib_py.delegation.finalize",
+    "lib_py.delegation.job_subscriber",
+    "lib_py.delegation.mqtt_common",
+    "lib_py.delegation.notifier",
+    "lib_py.delegation.publish_event",
+    "lib_py.delegation.publisher",
+    "lib_py.delegation.registry",
+    "lib_py.delegation.service",
+    "lib_py.delegation.cli",
+    # Agent adapter registry
+    "lib_py.agents.base",
+    "lib_py.agents.registry",
+    "lib_py.agents.input_region",
+    "lib_py.agents.sanitize",
+)
+
+OPTIONAL_MODULES: Sequence[str] = (
+    "yaml",
+    "paho.mqtt",
+    "paho.mqtt.client",
+)
+
+
+def verify_framework_version(expected_version: str = FRAMEWORK_VERSION) -> None:
+    """Verifies that MAM_VERSION matches framework version if set."""
+    env_version = os.environ.get("MAM_VERSION")
+    if env_version and env_version != expected_version:
+        raise RuntimeError(
+            f"MAM_VERSION mismatch: expected {expected_version}, got {env_version} in environment."
+        )
+
+
+def eager_load(
+    modules: Sequence[str] = CORE_MODULES,
+    optional_modules: Sequence[str] = OPTIONAL_MODULES,
+) -> List[str]:
+    """Eagerly imports all modules into sys.modules.
+
+    Returns the list of successfully loaded module names.
+    """
+    verify_framework_version()
+
+    # Ensure PYTHONDONTWRITEBYTECODE is set for isolation
+    sys.dont_write_bytecode = True
+    os.environ["PYTHONDONTWRITEBYTECODE"] = "1"
+
+    loaded: List[str] = []
+    for mod_name in modules:
+        if mod_name not in sys.modules:
+            try:
+                importlib.import_module(mod_name)
+            except Exception as exc:
+                raise RuntimeError(f"Failed to eager load {mod_name}: {exc}") from exc
+        loaded.append(mod_name)
+
+    for opt_mod in optional_modules:
+        if opt_mod not in sys.modules:
+            try:
+                importlib.import_module(opt_mod)
+                loaded.append(opt_mod)
+            except (ImportError, ModuleNotFoundError):
+                pass
+
+    return loaded
+
+
+def is_eager_loaded(modules: Sequence[str] = CORE_MODULES) -> bool:
+    """Returns True if all required core modules are present in sys.modules."""
+    return all(mod in sys.modules for mod in modules)