fix(macos): select format and frame-rate range from the same AVCaptureDeviceFormat

[kasper-cancilico]

Fixes #247.

Problem

AVCaptureDevice::set_all overwrites selected_format for every format matching the requested resolution, while selected_range may come from an earlier format. Applying a frame-rate range that does not belong to the new activeFormat makes AVFoundation throw NSInvalidArgumentException, which cannot unwind through the objc catch and aborts the process instead of returning Err. Cameras exposing several formats at one resolution (e.g. Logitech UVC devices: 420v + MJPEG variants) hit this deterministically in Camera::new().

Change

• Pick selected_format and selected_range together from the same AVCaptureDeviceFormat, breaking at the first pair that satisfies the requested fps (keeping the existing 0.999 tolerance for 29.97-style rates).
• Fall back to the first resolution-matching format with its first supported range when no fps match exists, instead of leaving a null/mismatched pair.
• lock(): set self.locked = true after a successful lockForConfiguration so unlock() (guarded by self.locked) actually calls unlockForConfiguration. Previously the flag was never set and the device stayed configuration-locked. This changes lock(&self) to lock(&mut self); the only in-tree caller (set_all) already takes &mut self.

Testing

• cargo check on nokhwa-bindings-macos (macOS 26, Apple Silicon): compiles; no new warnings.
• Hardware: Logitech USB webcam (VID 0x046D) that reproducibly aborted on Camera::new() with RequestedFormatType::AbsoluteHighestResolution now opens at 1280x960, streams frames continuously, and delivers full-resolution stills. A MacBook Air built-in camera and an iPhone Continuity camera still enumerate as before (open not re-tested on those).

🤖 Generated with Claude Code

[akx]

I implemented the same thing in 066c85a (#246) 👍