Add CSV output to dispatch notes list

[jongio]

Session notes are useful personal annotations, but dispatch notes list only has text and JSON output today.

Add CSV output so notes can be piped into spreadsheets, shell reports, or other CLI tools.

Acceptance criteria:

• dispatch notes list --csv prints id,summary,note rows.
• dispatch notes --csv works as a shortcut for the list command.
• CSV fields are escaped with the existing CSV safety pattern used elsewhere.
• Tests cover CSV output and invalid flag combinations.