feat(tool): support conditional parameter visibility

[zyqzyq]

Pull Request Checklist

Thank you for your contribution! Before submitting your PR, please make sure you have completed the following checks:

Compatibility Check

Part of langgenius/dify#36141.

• I have checked whether this change affects the backward compatibility of the plugin declared in README.md
• I have checked whether this change affects the forward compatibility of the plugin declared in README.md
• If this change introduces a breaking change, I have discussed it with the project maintainer and specified the release version in the README.md
• I have described the compatibility impact and the corresponding version number in the PR description
• I have checked whether the plugin version is updated in the README.md

Available Checks

• just build has passed
• Relevant documentation has been updated (if necessary)

No documentation or version update is needed for this additive schema change.

Summary

Tool parameters and their select options now preserve optional show_on conditions from plugin YAML.
Both fields default to an empty list so existing manifests remain unchanged.
A focused round-trip test covers parameter-level conditions, option-level conditions, and omitted fields.

Compatibility impact

This is an additive SDK schema change with no public method or runtime protocol removal.
Existing manifests continue to validate with empty show_on lists.
End-to-end UI support remains coordinated with langgenius/dify#36148 and langgenius/dify-plugin-daemon#732.

Validation

• uv run pytest tests/entities/test_tool.py -q (5 passed)
• just docs
• just check
• just test (185 passed, 1 skipped)
• just build

[gemini-code-assist]

Code Review

This pull request introduces a show_on field to the tool parameter configuration, enabling conditional display logic for parameters. The reviewer suggested adding a description attribute to this new field to maintain consistency with existing fields and ensure proper documentation generation.

[WH-2099]

Reviewed the schema contract against langgenius/dify#36148 and langgenius/dify-plugin-daemon#732. Field names, nesting, defaults, and the variable/value shape match. Local just check, just test, and just docs all pass; no blocking findings.