Add contacts by right-clicking anyone named in a message

Right-clicking a sender, or any address in the message details, opens a menu
offering to add that person to the address book - plus edit them when they are
already known, write to them, or copy the address.

"Add to contacts" opens the contact editor prefilled rather than saving
silently, so the address book gets a real card that the user can complete,
not a bare email address. contactFromAddress splits the display name into
JSContact name components: "Ada Lovelace" into given and surname, "Lovelace,
Ada" unpicked, a single word as the given name, and a name that is really
just an address left off entirely.

Addresses in the details block were joined into one string, so they are now
rendered per address to be individually targetable.

ContactEditor previously ignored a prefilled name on an unsaved card - it read
name components only when the card had an id - so it now reads them either
way.

README.md

@@ -32,6 +32,7 @@ ihasmail is a JMAP-first web client: mail, calendars, contacts, files, filters a
 - Messages sit on a light card by default, untouched as the sender designed them. *Appearance › Apply the theme to messages too* lets them follow the app's light/dark theme instead — plain-text mail always does, and with the option on so does HTML mail that brings no colours of its own; mail that styles itself is still left alone
 - Attachments: previews for images/PDF/text, download all, inline `cid:` images, `.eml` export, *Show original*, header viewer
 - Invitations: `.ics` parts render as an invite card with **Yes/Maybe/No** RSVP (via `CalendarEvent/parse` + iTIP); `.vcf` parts offer *Add to contacts*; `List-Unsubscribe` one-click
+- **Right-click anyone named in a message** — sender, To, Cc, Bcc, Reply-To — to add them to the address book (the contact editor opens prefilled, with the display name split into first/last), edit them if they are already known, write to them, or copy the address
 - Search with Gmail operators (`from:`, `to:`, `subject:`, `has:attachment`, `is:unread`, `is:starred`, `in:`, `label:`, `before:`, `after:`, `larger:`, `smaller:` …) plus an advanced-search panel
 - Composer: multiple floating/minimised/maximised composers, rich-text editor (formatting, lists, links, colours, images pasted/dropped inline, emoji), plain-text mode, recipient chips with autocomplete from **contacts, the directory (GAL) and recent recipients**, multiple identities with HTML signatures, Cc/Bcc, priority, read-receipt request, templates/canned responses, attachment upload with progress, drag & drop, attachment reminder, **undo send**, autosaved drafts, reply/reply-all/forward with quoting and inline images preserved
 - Live updates via JMAP push (EventSource proxied server-side) with polling fallback; desktop notifications, sound, title/favicon unread badge