Empirical failure: TypeError 281474976710655L is not JSON serializable from get_message_objects().
Root cause: previous per-attribute coercion only flattened known fields (severity/text/line); nested dicts/lists carrying CLR longs slipped through.
Fix: add a recursive _coerce_for_json helper that walks dicts/lists/tuples and downcasts long->int (or str if >Int64), keeps bool, then call it before every json.dumps in both compile_project.py and get_compile_messages.py.
Docs: https://content.helpme-codesys.com/en/ScriptingEngine/ScriptSystem.html (get_message_objects), https://content.helpme-codesys.com/en/ScriptingEngine/ScriptObject.html
Note: previous commit 418f678 added the per-field coercers; this commit
strengthens that with a recursive walker per the bug doc's proposal --
defensive against any future API change that nests longs deeper.
Manual smoke test only -- requires CODESYS-in-the-loop with a project
that produces compile messages whose severity bitmask is 0xFFFFFFFFFFFF.
### Manual smoke test
1. Open a project with at least one warning or error.
2. Call mcp__codesys__compile_project on it.
3. Expect SCRIPT_SUCCESS and a populated COMPILE_MESSAGES_START block;
no TypeError 'is not JSON serializable' anywhere in the output.
4. Repeat with mcp__codesys__get_compile_messages.
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