Fix Bezel fallback after interface load failure

[krahd]

Fixes a typo in the command-interface fallback path.

When the preferred command interface cannot be loaded, Quicksilver shows a notification saying it is switching to Bezel. The fallback code then asks the registry for QSBezelnterfaceController, which is missing the I in Interface.

That typo means the intended Bezel fallback can fail, leaving Quicksilver without a usable command interface after an interface/plugin load failure.

This changes the fallback key to QSBezelInterfaceController.

Context:

• This is relevant to recent macOS Tahoe reports where Quicksilver launches but has no usable interface, or shows “Interface could not be loaded. Switching to Bezel” and then remains crippled.
• This PR does not address file descriptor limits directly.
• This PR is separate from the optional-permissions startup gate PR.

[krahd]

Context from my Tahoe/macOS 26.5 setup:

• Quicksilver 2.6.0 showed interface/plugin failure symptoms around Primer and Bezel
• Logs included interface/plugin load failures and errno=24 / too many open files
• Switching manually to Bezel appeared to reduce or avoid the immediate interface failure
• The source appears to intend a Bezel fallback, but the key was misspelled as QSBezelnterfaceController

This PR only fixes the broken fallback key. It does not claim to solve the separate file-descriptor-limit problem directly.

[n8henrie]

Great catch, thanks!

This seems like the kind of bug that a stronger type system (or perhaps a language that makes its type system easier to leverage to "make invalid states unrepresentable") would help catch. My kingdom for a Rust (or maybe even Swift) rewrite of QS's core!

[n8henrie]

Thank you!