PR 10: Narrow meta-tool JSON coercion

[dsarno]

Summary

Base: beta

Addresses issue #297 finding #8 by narrowing nested JSON-string coercion in dispatch_manage_op().

The new policy is annotation-aware:

• Decode JSON-shaped nested strings only when the selected handler parameter expects a list/dict-like value.
• Preserve JSON-shaped strings unchanged when the handler parameter expects str.
• Raise GodotCommandError(ErrorCode.INVALID_PARAMS) for malformed JSON-shaped text or wrong JSON container type when the handler expects list/dict-like params, with data including tool, op, and param.
• Preserve existing handler TypeError wrapping for missing/extra arguments.

Compatibility is preserved for clients that stringify top-level manage params and for nested stringified list/dict values where the target handler annotation expects those containers.

PR 9 is being worked in parallel and this PR intentionally does not touch the GDScript self-update preload-alias scope.

Test Plan

• ruff check src/ tests/
• pytest -v (766 passed)
• pytest -q tests/unit/test_meta_tool.py tests/unit/test_middleware_parse_stringified_params.py tests/unit/test_middleware_op_typo_hint.py (36 passed)
• script/ci-check-gdscript
• script/ci-godot-tests attempted locally; it found a Godot session, then exited with curl code 7 while opening main.tscn. A follow-up probe showed no MCP server responding on 127.0.0.1:8000.

Out of Scope

• PR 9 preload-alias work
• Prepare PyPI packaging: metadata, --version flag, release-smoke CI #14 middleware ordering
• Coerce JSON-string list params on MCP tool boundary (fixes #11) #13 animation split
• Runtime Protocol work

[codecov]

Codecov Report

❌ Patch coverage is 92.10526% with 6 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/godot_ai/tools/_meta_tool.py	92.10%	6 Missing ⚠️

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