refactor(discussions): migrate to NewTool pattern

[SamMorrowDrums]

Summary

This PR continues the effort to eliminate NewServerToolLegacy wrappers by migrating discussions tools to the new NewTool pattern with ToolDependencies.

Changes

Converts all functions in discussions.go (4 functions):

• ListDiscussions
• GetDiscussion
• GetDiscussionComments
• ListDiscussionCategories

Updates the test file to use the new handler pattern.

Stack

• Depends on refactor(security): migrate code_scanning, secret_scanning, dependabot to NewTool pattern #1598

Pattern

Functions are converted from:

func FuncName(getGQLClient GetGQLClientFn, t translations.TranslationHelperFunc) (mcp.Tool, mcp.ToolHandlerFor[...])

To:

func FuncName(t translations.TranslationHelperFunc) toolsets.ServerTool {
    return NewTool(mcp.Tool{...}, func(deps ToolDependencies) mcp.ToolHandlerFor[...] {
        // Uses deps.GetGQLClient(ctx) instead of getGQLClient(ctx)
    })
}

Co-authored-by: Adam Holt omgitsads@users.noreply.github.com

[Copilot]

Pull request overview

This PR migrates discussion tools from NewServerToolLegacy wrappers to the modern NewTool pattern with ToolDependencies. The refactoring eliminates the need to pass getGQLClient as a function parameter, instead accessing it through the ToolDependencies struct injected via the handler factory pattern.

Key Changes:

• Converted 4 discussion functions to use NewTool with dependency injection
• Updated function signatures to return toolsets.ServerTool and accept only translation helper
• Modified all tests to use the new handler invocation pattern

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
pkg/github/discussions.go	Refactored all 4 discussion functions (ListDiscussions, GetDiscussion, GetDiscussionComments, ListDiscussionCategories) to use NewTool pattern with handler factory that accepts ToolDependencies
pkg/github/tools.go	Removed NewServerToolLegacy wrappers from discussion tools registration, now calling functions directly with translation helper
pkg/github/discussions_test.go	Updated all test cases to use new pattern: create toolDef, extract tool, create ToolDependencies, call toolDef.Handler(deps), and invoke handler without explicit params