fix: correct preemptive_compaction schema comment default value (#400)

The JSDoc comment incorrectly stated 'default: false' but since v2.9.0
preemptive compaction is enabled by default.

Fixes #398

Co-authored-by: sisyphus-dev-ai <[email protected]>

Author: sisyphus-dev-ai

src/config/schema.ts

@@ -172,7 +172,7 @@ export const DynamicContextPruningConfigSchema = z.object({
 export const ExperimentalConfigSchema = z.object({
   aggressive_truncation: z.boolean().optional(),
   auto_resume: z.boolean().optional(),
-  /** Enable preemptive compaction at threshold (default: false) */
+  /** Enable preemptive compaction at threshold (default: true since v2.9.0) */
   preemptive_compaction: z.boolean().optional(),
   /** Threshold percentage to trigger preemptive compaction (default: 0.80) */
   preemptive_compaction_threshold: z.number().min(0.5).max(0.95).optional(),