feat(proton-mail): Hermes skill — IMAP/SMTP tools via Bridge

Full Proton Mail Bridge Hermes skill with 6 tools:
- proton_mail_bridge_status — check daemon health
- proton_mail_list — list inbox/folder messages
- proton_mail_read — read full message by UID (body+headers)
- proton_mail_search — search by subject/from/body/all
- proton_mail_send — send email with CC/BCC support
- proton_mail_reply — reply preserving In-Reply-To/References

Implementation: pure Python stdlib (imaplib + smtplib + email),
no external dependencies. 22 unit tests with mocked IMAP/SMTP.

Follows architecture from ARCHITECTURE.md (section 3).
Per-tool auth via PROTONMAIL_ACCOUNT + PROTONMAIL_BRIDGE_PASSWORD env vars.
Bridge runs on 127.0.0.1:1143 (IMAP TLS) / 127.0.0.1:1025 (SMTP STARTTLS).

.gitignore

@@ -7,6 +7,12 @@ __pycache__/
 .env
 *.env.local
 
+# Python cache
+.pytest_cache/
+
+# Debug / scratch
+debug_*.py
+
 # OS
 .DS_Store
 Thumbs.db