chore(idea): translate the Chinese comments in jcef/, review/, messages/, model/ and the build script

Part of #1419. Ready to start — no open pull request touches extensions/idea/.

Scope

Translate the Chinese comments in the remaining idea main-source packages and in the build script (252 flagged lines across 15 files). Leave allowedPrefixes alone.

Files

Lines	File
31	.../idea/jcef/IdeaTheme.kt
18	.../idea/jcef/WebviewHtml.kt
16	.../idea/jcef/JcefReviewPanel.kt
15	.../idea/jcef/JcefConfigPanelHost.kt
14	.../idea/jcef/OcrWebview.kt
26	.../idea/review/ReviewProjectService.kt
26	.../idea/review/SidebarRouter.kt
19	.../idea/review/ConfigPanelRouter.kt
7	.../idea/review/ConfigPanelHost.kt
19	.../idea/messages/WebviewMessages.kt
12	.../idea/messages/HostMessages.kt
10	.../idea/model/Types.kt
7	.../idea/model/Locale.kt
2	.../idea/toolwindow/OcrToolWindowFactory.kt
30	extensions/idea/build.gradle.kts

Two things worth preserving carefully:

• build.gradle.kts explains why npm is resolved to an absolute path rather than invoked as npm (nvm installs it only on the login shell's PATH, and Gradle launched from a GUI IDEA sees a reduced PATH). It also explains the -PskipFrontend=true escape hatch and why doFirst/onlyIf blocks must only use local variables.
• jcef/ explains the fallback path when the runtime has no JCEF support.

Locale.kt's comment notes that the serialised values must stay the literals en and zh-cn; keep that warning intact.

Done when

• Temporarily dropping the extensions/idea/ exemption no longer reports any of these files.
• ./gradlew test -PskipFrontend=true and ./gradlew verifyPluginStructure -PskipFrontend=true pass.