The prior null-safe esc patch only matched 'const esc =' declarations;
Menu/Navbar/Logo use 'function esc(str: string)' syntax and slipped
through. Patched those three to coerce non-strings the same way.
Added "Clear chat" button in the modal header that appears when there's
any message history. Confirms with the user before posting to the new
clear_history endpoint, which deletes all messages + the thread row
for the current site (usage rows are preserved for billing).
Josh Knapp
906695379b