Fix flaky nightly CI: bump main-actor blocking threshold from 0.2 to 0.3 (#185)

testStartRecordingDoesNotBlockMainActorDuringAudioStart was failing
intermittently on CI runners where initial MainActor work (guard checks,
state mutation, cursor overlay) took 204ms — just over the 0.2s limit.

The mock audio engine's startRecordingDelay is 0.3, so the test intent is
to verify the main actor doesn't synchronously wait for the full audio
start duration. Matching the threshold to the mock delay (0.3) preserves
the assertion while eliminating the timing flake.

Author: jatinkrmalik

Tests/VocaMacTests/AppStateRecordingTests.swift

@@ -46,7 +46,7 @@ final class AppStateRecordingTests: XCTestCase {
         await Task.yield()
         try await Task.sleep(nanoseconds: 50_000_000)
 
-        XCTAssertLessThan(Date().timeIntervalSince(start), 0.2,
+        XCTAssertLessThan(Date().timeIntervalSince(start), 0.3,
                           "Core Audio startup should not block the main actor")
 
         await task.value