Code quality (#142)

Write strict ISO C: C99, as the driver builds (-std=c99 -pedantic-errors), unless the target needs more. C99 is the baseline, so use what it has: static inline functions, <stdint.h> types (SnxU32/SnxU64 in the driver), 64-bit literals as 0x...ull (not UINT64_C, not two halves), SIZE_MAX in size checks (n > SIZE_MAX / size), %zu for a size_t, %llu/%llx through (unsigned long long) for a 64-bit value (never (unsigned long): long is 32 bits on Windows), bool or int flags, strtoull, snprintf. A declaration may follow statements and open a for; comments stay /* */, as the code has them. In place of C11 and C23: __atomic_* builtins on plain integers, a char padding array, a negative-size array typedef as the static assert. A file's build flags plus -std=c99 -pedantic list what is not. A local that starts zeroed is declared = {0}, not zeroed by a memset after its declaration; a memset stays for an object reached through a pointer. strdup is not C99: snx_strdup (common.h) is, and fails the way the rest of the code does when memory runs out.

1. No state another value already says. A NULL pointer is absent: no is_present beside it. Not when NULL means something itself, or the flag says something else.
2. Indices, not pointer chains. Objects in one array, linked by u32 index; 0 is none, so slot 0 is never an object. Not when the index can outlive its array.
3. One allocation per owner. An owner's arrays come from one block carved by offsets (each at a multiple of its type's size), sizes checked against (size_t)-1, one free. Not for an array that grows on its own, or parts that live apart.
4. Atomics apart. Atomics that different threads write get a cache line each (a char pad between). Not when one thread writes them all, or for many per-object atomics.
5. No stored pointers in data. Data refers to its parts by index or offset, so a copy or a file holds together. Handles (FILE*, SDL, Vulkan) stay in a runtime struct beside it.
6. One global per file. A file's mutable state (every variable of static duration, function-local statics included) is the members of one struct in one global, g_<file>, not loose globals. What other files read is declared once, in the header beside it, through the struct or a function. Not for const tables (they are data, not state), or for _Thread_local. In src/nx/hle/ the HLE's state is one global for the whole subsystem: each file's state struct is a member of g_hle (hle/hle.h), its type and initializer declared in the header beside the file, and the objects it makes and frees come from bounded pools in it (an all-zero slot is free, pool_take searches on from the last slot taken and asserts when full). No file there defines a variable of static duration.

Review: python3 .claude/skills/snx-code-quality/check.py FILES lists candidates for 1, 3, 4 and 6 (a candidate is not a finding until the code is read); read the diff for 2 and 5. Report file:line, the rule and the fix. A rule that does not apply is not a finding. Wrong and right C for each rule: examples.md.