Day 138: One Mailbox Interface, Two Providers

Pinchy's email support was Gmail-shaped down to the bone, raw label strings and raw Gmail query syntax leaking straight into the agent's world. Adding Microsoft 365 (PR #328) forced the right refactor first: a single EmailAdapter contract of list, read, search, draft, and send, with canonical folder names (INBOX, SENT, DRAFTS, TRASH, SPAM) and a structured search DSL that neither Gmail nor Graph…