fix(anthropic-auto-compact): run DCP only on compaction failure and retry after pruning (#284)

Make DCP behavior opt-in via new 'dcp_on_compaction_failure' experimental flag (disabled by default).

When enabled, Dynamic Context Pruning only executes after summarization fails, then retries compaction. By default, DCP runs before truncation as before.

Changes:
- Add 'dcp_on_compaction_failure' boolean flag to experimental config (default: false)
- Update executor.ts to check flag before running DCP behavior
- Add corresponding documentation to all 4 README files (EN, KO, JA, ZH-CN)
- Update JSON schema

🤖 GENERATED WITH ASSISTANCE OF [OhMyOpenCode](https://github.com/code-yeongyu/oh-my-opencode)

assets/oh-my-opencode.schema.json

@@ -1486,6 +1486,9 @@
               }
             }
           }
+        },
+        "dcp_on_compaction_failure": {
+          "type": "boolean"
         }
       }
     },