feat: added assistant message event interception for streaming edit abort control

- Added `onAssistantMessageEvent` callback to Agent API for inspecting and aborting assistant streaming events.
- Added `setAssistantMessageEventInterceptor()` method to dynamically update assistant message event handlers.
- Converted `checkAutoGeneratedFileContent()` from async to synchronous for improved streaming edit abort detection performance.
- Implemented LRU caching in auto-generated file detection with early path-based checks to prevent unnecessary edits.
- Refactored streaming edit pre-caching to use assistant message event interception for real-time abort capability.
- Extracted `peekFile()` utility for efficient file prefix reading with pooled buffer reuse strategy.

packages/coding-agent/CHANGELOG.md

@@ -1,8 +1,12 @@
 # Changelog
 
 ## [Unreleased]
+
 ### Changed
 
+- Made `assertEditableFileContent` synchronous instead of async for improved performance in streaming edit checks
+- Enhanced streaming edit abort detection to check for auto-generated files as soon as the file path is available, rather than waiting for the full diff
+- Improved file prefix reading in session storage to use `peekFile` utility from @oh-my-pi/pi-utils for better efficiency
 - Moved image metadata detection to @oh-my-pi/pi-utils package for shared use across projects
 - Simplified image loading API by removing redundant metadata parameters and consolidating image utilities
 - Updated imports to use readImageMetadata and parseImageMetadata from @oh-my-pi/pi-utils instead of local implementations
@@ -13,6 +17,10 @@
 - Removed mime.ts utility module; MIME detection moved to @oh-my-pi/pi-utils
 - Removed ImageMetadata interface and ReadImageMetadataOptions from local codebase
 
+### Fixed
+
+- Fixed streaming edit abort for auto-generated files by adding LRU caching and early path-based detection to prevent unnecessary edits
+
 ## [14.0.0] - 2026-04-08
 
 ### Breaking Changes