feat(compaction): make post-compaction context sections configurable (#34556)

Merged via squash.

Prepared head SHA: 491bb28544
Co-authored-by: efe-arv <259833796+efe-arv@users.noreply.github.com>
Co-authored-by: jalehman <550978+jalehman@users.noreply.github.com>
Reviewed-by: @jalehman

src/config/types.agent-defaults.ts

@@ -314,6 +314,12 @@ export type AgentCompactionConfig = {
   qualityGuard?: AgentCompactionQualityGuardConfig;
   /** Pre-compaction memory flush (agentic turn). Default: enabled. */
   memoryFlush?: AgentCompactionMemoryFlushConfig;
+  /**
+   * H2/H3 section names from AGENTS.md to inject after compaction.
+   * Defaults to ["Session Startup", "Red Lines"] when unset.
+   * Set to [] to disable post-compaction context injection entirely.
+   */
+  postCompactionSections?: string[];
 };
 
 export type AgentCompactionMemoryFlushConfig = {