Sanity tests: stop constructing a second ConversationFeature

[benvillalobos]

Sanity tests currently construct their own ConversationFeature and force activated = true synchronously, in addition to the global one that ContributionCollection creates during extension activation. Both instances react to onDidAuthenticationChange and try to register global ids (e.g. the copilot-chat.fixWithCopilot terminal quick-fix provider, chat participants), which races and produces flaky already registered failures — sometimes synchronously during new ConversationFeature() in the test, sometimes asynchronously from the global's auth listener firing inside a Timeout._onTimeout.

This change removes the test-local ConversationFeature entirely. suiteSetup now:

• awaits IAuthenticationService.getCopilotToken() so the Copilot token is minted, then
• waits briefly for onDidAuthenticationChange listeners to run, which flips the global ConversationFeature to activated = true (registering chat participants and other global state) before any test runs.

Tests then use ChatParticipantRequestHandler directly against the production-activated global feature, which is what the real chat flow does anyway.

Net effect: only one ConversationFeature exists at runtime, eliminating the registration race. Companion to #316709 (Mocha retries) and #316719 (proper dispose in finally).

[Copilot]

Pull request overview

Removes the test-local ConversationFeature instances from sanity tests to eliminate a race with the globally-activated ConversationFeature registered by ContributionCollection during extension activation. Instead, suiteSetup mints a Copilot token to drive the global feature's auth listeners to flip activated = true before tests run.

Changes:

• Import IAuthenticationService; remove ConversationFeature import.
• In suiteSetup, call getCopilotToken() and wait 500ms so the global ConversationFeature gets activated.
• Drop per-test ConversationFeature creation and try/finally activated toggling across all four tests.

Show a summary per file

File	Description
extensions/copilot/src/extension/test/vscode-node/sanity.sanity-test.ts	Replace per-test ConversationFeature setup with a one-time token mint + brief wait in suiteSetup so the global ConversationFeature activates once.

Copilot's findings

• Files reviewed: 1/1 changed files
• Comments generated: 0

[Copilot]

Copilot's findings

• Files reviewed: 1/1 changed files
• Comments generated: 0 new

[Copilot]

Copilot's findings

• Files reviewed: 1/1 changed files
• Comments generated: 0 new