Report cases where we can't find *any* terminal on the system

This should only happen in extreme environments (perhaps Linux with no
common terminal emulators installed whatsoever), or notably on OSX if
Spotlight is disabled. Reporting this will let us check if that case is
common, and help decide if it's worth investigating it further.

Author: pimterry

src/interceptors/terminal/fresh-terminal-interceptor.ts

@@ -368,7 +368,9 @@ export class TerminalInterceptor implements Interceptor {
     constructor(private config: HtkConfig) { }
 
     async isActivable(): Promise<boolean> {
-        return !!(await getTerminalCommand());
+        const terminalAvailable = !!(await getTerminalCommand());
+        if (!terminalAvailable) reportError('No terminal could be detected');
+        return terminalAvailable;
     }
 
     isActive(proxyPort: number | string): boolean {