refactor: rename stale HTTPDaemonClient test file to ConversationForkDecodingTests

[devin-ai-integration]

Summary

Renames HTTPDaemonClientConversationForkDecodingTests.swift → ConversationForkDecodingTests.swift and aligns the class name to match. HTTPDaemonClient was removed from the codebase as part of the GatewayHTTPClient migration (#21729), leaving this test file with a stale name. The class inside had already been partially renamed to GatewayConnectionManagerConversationForkDecodingTests, but these tests actually decode shared model types (ConversationsListResponse, ConversationListResponse, ForkConversationResponse) — they aren't specific to any client or manager. The new name reflects what they actually test.

No logic changes. Zero references to the old filename or class name exist elsewhere (verified via grep).

Review & Testing Checklist for Human

• Run the test target in Xcode to confirm ConversationForkDecodingTests is discovered and all 5 tests pass after the rename

Notes

• Flagged by Devin Review on docs: scope @MainActor guidance to UI state types and remove stale DaemonClient references #21777 as a follow-up consistency item

Link to Devin session: https://app.devin.ai/sessions/e19a9c46f61546368efaba6020397e17
Requested by: @ashleeradka

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✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no bugs or issues to report.