Images: All signatures use Google Drive hosted URLs.
If images break in certain email clients (Drive's virus-scan interstitial),
re-host on this15fine.dev and update the URLs in the
HOSTED_HEADSHOT and HOSTED_CLAUDE constants
in the HTML source.
Dark mode: Email clients invert differently —
Gmail swaps backgrounds, Apple Mail does full dark stylesheets,
Outlook improvises. Text colors here are chosen to maintain
≥4.5:1 contrast across all modes.