docs: accept leader summary notification architecture

.project-docs/60-reflection/cases/20260907-integrate-leader-summaries-84c1d7ea__integration-source-baseline.md

@@ -0,0 +1,19 @@
+# Reflection: Integration source baseline
+
+## Trigger
+
+The first leader-summary Integration worktree was created from `origin/main` and then merged the completed Feature commit. Because `check_doc_drift.py` compares the Integration tree with its recorded base, the Feature's required task record appeared as a foreign task-owned change even though Integration had not edited it.
+
+## Lesson
+
+For one completed Feature, the Integration task should start from the Feature commit that already contains its task record. The target default branch must then be verified as an ancestor or reconciled before canonical edits. This preserves the source record as read-only while making the drift boundary mechanically accurate.
+
+## Action
+
+- Restarted the Integration task from source commit `1a3ab63` after preserving the first attempt and normally releasing its lock.
+- Added the single-Feature baseline rule to `.project-docs/05-agent-entry/integration-gate.md`.
+- Kept the occupied `main` worktree untouched and used no force, reset, stash, or history rewrite.
+
+## Reuse
+
+Apply this baseline choice to future one-Feature integrations. Multiple-source integrations still require an explicitly reviewed combined strategy; do not bypass foreign task-record checks.