chore: improve type safety in session-tool-result-guard-wrapper

[mgabrielramos]

Refactored src/agents/session-tool-result-guard-wrapper.ts to replace any with AgentMessage.

This improves type safety and maintainability by ensuring that the transform function in guardSessionManager correctly types the message parameter.

Verified by running existing tests:

• src/agents/session-tool-result-guard.tool-result-persist-hook.test.ts
• src/agents/session-tool-result-guard.test.ts
  All tests passed. Also ran oxlint and oxfmt checks.

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PR created automatically by Jules for task 2817787361048174822 started by @mgabrielramos

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