fix: centralize file path validation for tools

[msnandhis]

Fixes #2138.

Summary

This centralizes workspace-root validation for request file path fields instead of having individual tool handlers call context.validatePath(...) directly.

Changes included:

• add required annotations.filePathFields metadata to tool definitions
• validate annotated request fields centrally in ToolHandler before handler execution
• annotate existing tools that accept request path fields such as filePath, requestFilePath, responseFilePath, outputDirPath, and extension path
• remove duplicated per-tool validation calls for direct request path fields
• keep non-request validation in reload_extension, because that path is resolved from existing extension state rather than from request params
• add ToolHandler coverage to ensure annotated file path fields are validated before the handler runs

Testing

• npm run format
• npm run check-format
• npm run test tests/ToolHandler.test.ts

I also started a full npm run test; it built and ran many tests locally, then remained quiet in a daemon/browser section, so I stopped the local run and cleaned up the spawned daemon processes rather than leaving them running.

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[OrKoN]

Thanks for the PR, we discussed it offline and we actually want to move filePathFields to the same level as blockedByDialog (i.e., outside of annotations). cc @Lightning00Blade