feat: upgrade to Zod v4 and use native JSON schema generation

[chentsulin]

Summary

• Upgrade zod from ^3.25.16 to ^4.3.5
• Upgrade @modelcontextprotocol/sdk from ^1.11.4 to ^1.25.2
• Remove zod-to-json-schema dependency and migrate to Zod v4's native toJSONSchema() method

Changes

This PR modernizes our dependency stack by adopting Zod v4, which includes native JSON schema generation capabilities. This allows us to remove the external zod-to-json-schema package, reducing dependencies and using the official Zod v4 API.

Key changes:

1. Dependency updates: Updated Zod to v4.3.5 and MCP SDK to v1.25.2
2. Schema generation: Migrated from zod-to-json-schema to Zod's native toJSONSchema() method
3. Code cleanup: Removed the TODO comment as Zod v4 is now stable

Test plan

• Verify all existing functionality works with the new Zod v4 API
• Test JSON schema generation produces expected output
• Run test suite to ensure no regressions
• Verify MCP SDK compatibility with updated version

[gemini-code-assist]

Summary of Changes

Hello @chentsulin, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request modernizes the project's dependency stack by upgrading Zod to its fourth major version and updating the Model Context Protocol SDK. The primary impact is the simplification of JSON schema generation, moving from an external library to Zod v4's native toJSONSchema() method, which reduces the project's external dependencies and streamlines the schema generation process.

Highlights

• Dependency Upgrade (Zod): Zod has been upgraded from version ^3.25.16 to ^4.3.5, bringing in its native JSON schema generation capabilities.
• Dependency Upgrade (MCP SDK): The @modelcontextprotocol/sdk dependency has been updated from ^1.11.4 to ^1.25.2.
• Simplified JSON Schema Generation: The external zod-to-json-schema library has been removed, and the project now utilizes Zod v4's built-in toJSONSchema() method for generating JSON schemas.
• Code Cleanup: A TODO comment regarding Zod v4 stability in src/utils/schema.ts has been removed as Zod v4 is now stable and in use.

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[gemini-code-assist]

Code Review

This pull request successfully upgrades Zod to v4 and migrates from zod-to-json-schema to the native toJSONSchema method, which is a great modernization step. The dependency changes in package.json are correct. My review focuses on src/utils/schema.ts, where I've identified a couple of important behavioral changes resulting from this migration related to the generated JSON schema. I've provided a suggestion to align the new implementation with the previous behavior where appropriate and to improve code clarity.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.01%. Comparing base (0bd0233) to head (0727f20).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #254      +/-   ##
==========================================
- Coverage   81.02%   81.01%   -0.01%     
==========================================
  Files          42       42              
  Lines        1982     1981       -1     
  Branches       31       31              
==========================================
- Hits         1606     1605       -1     
  Misses        374      374              
  Partials        2        2              

Files with missing lines	Coverage Δ
src/utils/schema.ts	100.00% <100.00%> (ø)

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[hustcc]

fixed #163