What's the difference between hard-boiled fiction and crime fiction?

I'm seriously confused now. I just read (in Wikipedia) that detective fiction is a sub-genre of both crime fiction and mystery. Now there's this hard-boiled thing. Those money-grubbing editors and critics only do this to annoy, I think.

Crime fiction covers a broad range of writing about crime and the people involved in criminal activity -- the police, private detectives, criminals, lawyers, and so on. The plots range from the solving of the mystery of who committed the crime (a so-called "whodunit"), to following the police in their activities (a police procedural), to the semi-humorous antics of ordinary citizens and amateur detectives (the "cozy").

The hard-boiled genre are gritty stories of the criminal underworld, usually containing sex, violence, and corruption (both public and private). The famous authors of the genre -- Hammett and Chandler -- wrote from the point of view of a protagonist who was a lone private detective, tough but honest and determined to unravel the mystery of a murder in the face of deceitful women and uncooperative clients.

People who study this kind of thing differentiate hard-boiled from noir by noting that the former describes style and the latter, content. Noir is dark and grim, no matter its style. Hard-boiled is gritty and unsentimental, no matter its outlook. Details in a discussion here. There are numerous works where the two overlap, and it's certainly possible to have a story that's hardboiled or grim or both but that doesn't involve crime, but the terms are usually associated with crime fiction.

Why hard boiled? Perhaps it was the attraction of "hard" meaning tough and "boiled" meaning inured to heat. Perhaps it was metaphoric from the tough exterior of a hard-boiled egg. In any case, this was a popular term in the 1920s to describe people from purchasing agents to sled dogs. And it gave rise to this illustrative pun from Colliers Illustrated Weekly from 1926:

Pancho Villa, champion of all the hard-boiled yeggs^*, wasn't in on this, but his brother Hipolito got Bud and his friends safely over the border.

In the same year archetypical hard-boiled author Ernest Hemingway used the term in The Sun Also Rises:

“It is awfully easy to be hard-boiled about everything in the daytime, but at night it is another thing.”

It's possible that the term arose from the invention of the E.D. Bullard Company, was a mining equipment manufacturer, which in 1919 patented a precursor to the modern hard hat, a "hard-boiled hat" made of steamed canvas, glue and black paint.

Noir is no mystery (so to speak); it's French for black.

* A yegg is underworld cant for a thief or burglar, especially a safecracker.