Summary

• Tighten the Data Machine-to-Agents API context handoff so top-level host payload fields win over same-named client_context keys.
• Add focused smoke/unit assertions for explicit client_context_bindings reading authoritative host payload values.

Follow-up to #2594 after a self-review pass on #2592.

Tests

• php tests/tool-source-registry-smoke.php passed: all 63 assertions.
• php -l inc/Engine/AI/Tools/ToolExecutor.php passed.
• php -l tests/tool-source-registry-smoke.php passed.
• php -l tests/Unit/AI/Tools/ToolExecutorValidationTest.php passed.

AI assistance

• AI assistance: Yes
• Tool(s): OpenCode (openai/gpt-5.5)
• Used for: Performed a self-review pass, identified the host/context precedence edge case, implemented the small follow-up, and ran focused verification. Chris remains responsible for review and testing.