copilot: Avoid Node deprecation warnings

[connor4312]

Summary

• update @google/genai to the first v1 release that uses google-auth-library@10
• remove the transitive node-fetch@2, whatwg-url, and tr46 dependency chain from the bundled Copilot extension
• prevent DEP0040 (punycode) and DEP0169 (url.parse()) warnings from appearing in Extension Development Host debug sessions

Fixes #328548

Validation

• npm run compile in extensions/copilot
• npm run typecheck in extensions/copilot
• focused Gemini unit tests: 35 passed, 3 skipped
• verified the rebuilt dependency bundle is silent under Electron with --trace-deprecation

[Copilot]

Pull request overview

Updates Copilot’s Gemini SDK dependency to eliminate Node deprecation warnings from its bundled authentication stack.

Changes:

• Upgrade @google/genai to 1.26.
• Replace the deprecated node-fetch@2 dependency chain.

Show a summary per file

File	Description
extensions/copilot/package.json	Updates the Gemini SDK dependency.
extensions/copilot/package-lock.json	Locks updated Google authentication and fetch dependencies.

Review details

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• extensions/copilot/package-lock.json: Generated file

• Files reviewed: 1/2 changed files
• Comments generated: 0
• Review effort level: Balanced