docs: update for partio-io/cli#10

Automated documentation update by partio-io/minions doc-minion.
Source PR: partio-io/cli#10

Co-Authored-By: Claude <noreply@anthropic.com>

Author: minion[bot]

core-concepts.mdx

@@ -12,7 +12,9 @@ A **session** is a single AI agent conversation — from the time you start inte
 - **Full transcript** — the complete JSONL conversation log
 - **Context summary** — a markdown summary of what was discussed
 - **Initial prompt** — the first prompt that started the session
-- **Metadata** — agent name, token count, duration
+- **Metadata** — agent name, token count, duration, files modified
+
+Files listed in `.gitignore` (including nested and global gitignore rules) are automatically excluded from the files modified list.
 
 ## Checkpoints