Background ReadAction Freeze Companion

Not the usual "a paid competitor's users are complaining" story this catalog is built around -- this one is motivated directly by JetBrains' own Platform Blog:

• ["Investigating IntelliJ Platform UI Freezes"](https://blog.jetbrains.com/platform/2025/09/investigating-intellij-platform-ui-freezes/) (Sept 2025): detecting a freeze today is manual, post-mortem thread-dump analysis, after it already happened in a real user's IDE.
• ["UI Freezes and the Dangers of Non-Cancellable Read Actions in Background Threads"](https://blog.jetbrains.com/platform/2026/03/ui-freezes-and-the-dangers-of-non-cancellable-read-actions-in-background-threads/) (March 2026): "many reports actually show problems in plugins that contain that single erroneous pattern" -- a background thread calling ReadAction.compute()/ReadAction.run()/Application#runReadAction(), none of them cancellable, blocking the write lock and freezing the UI. The post gives a real code example and names a real plugin ("Package Checker") affected by it. It states plainly that there's no static tool for this today.

Verified independently (not just taken on the blog's word): neither the official Plugin Verifier (bytecode compatibility, not locking semantics) nor any of the 8 new Kotlin coroutine inspections shipped in IDEA 2025.2-2026.1 cover this pattern.