refactor(agent): unified transcript block finalization logic

- Replaced commit-based stability checks with a unified `isTranscriptBlockFinalized` tracking mechanism.
- Removed deprecated provisional rendering configuration and flags across tool and renderer interfaces.
- Standardized native scrollback boundary logic to pin at the first unfinalized block using settled row verification.
- Updated and refactored test suites to validate block finalization and settled row boundaries instead of deprecated commit stability methods.

packages/coding-agent/src/tools/bash.ts

@@ -1409,10 +1409,6 @@ export function createShellRenderer<TArgs>(config: ShellRendererConfig<TArgs>) {
 		},
 		mergeCallAndResult: true,
 		inline: true,
-		// Collapsed pending preview caps the command to a viewport-sized tail
-		// window that shifts while args stream. Expanded output is top-anchored
-		// enough for the transcript to commit its settled prefix.
-		provisionalPendingPreview: "collapsed",
 	};
 }