ai: apply changes for #499 (1 review thread)

Addresses:
  - #3771964358 at .bot/config.yaml:103

Signed-off-by: peco-engineer-bot[bot] <peco-engineer-bot[bot]@users.noreply.github.com>

Author: peco-engineer-bot[bot]

.claude/knowledge/learning-log.md

@@ -0,0 +1,12 @@
+# Engineer-bot learning log
+
+This file is the shared knowledge log for the databricks-sql-nodejs engineer-bot.
+
+- The **retrospective** flow (see `.bot/config.yaml` → `retrospective.log_path`)
+  appends a dated section here whenever it distills a durable, reusable learning
+  from merged PRs and author runs.
+- The **author** flow (see `.bot/config.yaml` → `author.knowledge_log`) reads this
+  file back so fixes benefit from what the retrospective has learned.
+
+No learnings have been recorded yet — the first retrospective PR will append the
+initial dated section below.