chore(idea): translate the plugin's Chinese test names and drop the exemption

Part of #1419. Merge last — this issue deletes the extensions/idea/ exemption, so it needs #1421, #1422 and #1423 merged first.

Scope

Translate the Chinese test names and comments under extensions/idea/src/test/ (448 flagged lines across 18 files), then delete the extensions/idea/ entry from allowedPrefixes in scripts/verify-english-only.go.

Most of these are Kotlin backtick-quoted test names. The work is mechanical but large, so keep the translations literal and consistent across files.

Files

Lines	File (under .../idea/)
65	services/GitMapTest.kt
45	messages/WebviewMessagesTest.kt
35	services/ConfigDraftTest.kt
32	jcef/WebviewHtmlTest.kt
32	model/HostStringsTest.kt
32	providers/CommentAnchorTest.kt
29	messages/MessageContractTest.kt
26	messages/HostMessagesTest.kt
26	services/CliParseTest.kt
25	OcrBundleTest.kt
18	jcef/IdeaThemeTest.kt
18	services/ConfigParseTest.kt
13	services/ConfigUtilsTest.kt
12	services/ProvidersTest.kt
11	services/ShellEnvTest.kt
10	services/CliServiceTreeKillTest.kt
10	services/ReviewSessionTest.kt
9	FrontendSources.kt

OcrBundleTest.kt compares the OcrBundle.properties key sets; HostStringsTest.kt does the same for HostStrings. Their assertions reference Chinese values on purpose — keep the expected values, translate only the names and comments around them.

Done when

• make check passes with no extensions/idea/ entry in allowedPrefixes, leaving only the narrow HostStrings.kt exemption from #1423.
• ./gradlew test -PskipFrontend=true passes.
• The repo-wide count from #1419 reaches zero.