ci(linux): add reproducible kernel module build matrix

[pvurda]

Summary

• add Linux module CI for Ubuntu 22.04 / kernel 5.15, Ubuntu 24.04 / kernel 6.8, and Ubuntu 24.04 / kernel 6.14 HWE headers
• build with W=1, validate the x86-64 module with file and modinfo, and retain build evidence as artifacts
• add changed-line whitespace and Linux checkpatch.pl validation
• make clean work without kernel headers and remove shared codec artifacts outside linux/

No runtime or device-support changes.

Local validation

Validated on Ubuntu 24.04 against /lib/modules/6.14.0-37-generic/build:

• make -C linux ci KERNELDIR=/lib/modules/6.14.0-37-generic/build
• modinfo linux/snd-usb-ozzy.ko reports snd_usb_ozzy
• file reports an ELF 64-bit LSB relocatable x86-64 module
• make clean leaves no .o, .ko, .cmd, Module.symvers, or modules.order artifacts
• workflow passes actionlint 1.7.12 and YAML parsing

CI artifacts

Each build variant uploads for 14 days:

• snd-usb-ozzy.ko
• build.log with compiler, Make, package, and header versions
• modinfo.txt
• file.txt

[pvurda]

Fork CI is green after the follow-up fix: https://github.com/pvurda/Ozzy/actions/runs/32913685382

Validated checks:

• build-ubuntu-22.04
• build-ubuntu-24.04
• build-ubuntu-24.04-hwe (6.14.0-37 headers)
• static-checks

All three artifact bundles were downloaded and verified to contain the module, build log, modinfo, and file output.