Pasting a list of addresses into To/Cc/Bcc now creates one chip per
address instead of dropping the whole blob in as a single invalid chip.
A paste is split only when it actually contains a separator; a lone
address falls through to normal editing.
- Separators: commas, semicolons, and any whitespace/newline - covers
comma/space dumps, spreadsheet columns and Outlook-style `;` lists.
- Display names are preserved: `Name <email>`, a fully-quoted
`"Name <email>"` entry, and `"Doe, John" <email>` (comma inside a
quoted name) each stay a single chip with the name intact.
- Bare-address runs split per address; a `<addr>` token is unwrapped;
tokens that aren't valid addresses are left behind in the input for
the user to fix rather than becoming junk chips.
- Deduped case-insensitively within the paste and against existing chips.
Implemented as splitPastedRecipients in email-composer-utils, layered on
the shared quote/angle-aware splitter: splitRecipients gains an optional
`separators` argument so the composer/mailto serialization boundary
(comma-only) and the paste path (`,;\n\r`) share one implementation.
Wired into the recipient chip input's onPaste handler (To/Cc/Bcc).
Linus Rath