libSceJxr technical debt

PixelFormatLookup is listed in the PS5 3.20 export table and was cross-checked against firmware 13.60. Its signature and behaviour remain unverified; the declaration uses the no-parameter unknown-signature convention and throws through NotImplemented_nid_no_patch.

PKFree (libSceJxr) follows Microsoft's jxrlib JXRGlue.c, whose four exported names the module shares: a non-null ppv has *ppv released with the guest free and set to null, and the result is always WMP_errSuccess (0) as a 64-bit ERR (long). That the console's module is built from jxrlib, and that its PKFree releases through libc's free, is inferred from the export names and not checked against the console's code. Closes when: the console's PKFree is disassembled or measured on a PS5
readIS and writeIS use the non-ARM, LP64 BitIOInfo and WMPStream ABI and packet algorithm from Microsoft's JPEG XR reference implementation. Console structure layouts and execution remain unverified. Profiling callbacks are omitted as in the reference Unix build with DISABLE_PERF_MEASUREMENT; the codec argument is unused. Invalid null state or required callbacks throw instead of dereferencing them. No codec is instantiated by these helpers; callers must supply the reference ring buffer and guest-ABI stream callbacks.