fix: flush block streaming on paragraph boundaries for chunkMode=newline (#7014)

* feat: Implement paragraph boundary flushing in block streaming

- Added `flushOnParagraph` option to `BlockReplyChunking` for immediate flushing on paragraph breaks.
- Updated `EmbeddedBlockChunker` to handle paragraph boundaries during chunking.
- Enhanced `createBlockReplyCoalescer` to support flushing on enqueue.
- Added tests to verify behavior of flushing with and without `flushOnEnqueue` set.
- Updated relevant types and interfaces to include `flushOnParagraph` and `flushOnEnqueue` options.

* fix: Improve streaming behavior and enhance block chunking logic

- Resolved issue with stuck typing indicator after streamed BlueBubbles replies.
- Refactored `EmbeddedBlockChunker` to streamline fence-split handling and ensure maxChars fallback for newline chunking.
- Added tests to validate new chunking behavior, including handling of paragraph breaks and fence scenarios.
- Updated changelog to reflect these changes.

* test: Add test for clamping long paragraphs in EmbeddedBlockChunker

- Introduced a new test case to verify that long paragraphs are correctly clamped to maxChars when flushOnParagraph is enabled.
- Updated logic in EmbeddedBlockChunker to handle cases where the next paragraph break exceeds maxChars, ensuring proper chunking behavior.

* refactor: streamline logging and improve error handling in message processing

- Removed verbose logging statements from the `processMessage` function to reduce clutter.
- Enhanced error handling by using `runtime.error` for typing restart failures.
- Updated the `applySystemPromptOverrideToSession` function to accept a string directly instead of a function, simplifying the prompt application process.
- Adjusted the `runEmbeddedAttempt` function to directly use the system prompt override without invoking it as a function.

src/auto-reply/reply/agent-runner-execution.ts

@@ -63,6 +63,7 @@ export async function runAgentTurnWithFallback(params: {
     minChars: number;
     maxChars: number;
     breakPreference: "paragraph" | "newline" | "sentence";
+    flushOnParagraph?: boolean;
   };
   resolvedBlockStreamingBreak: "text_end" | "message_end";
   applyReplyToMode: (payload: ReplyPayload) => ReplyPayload;