style(string): satisfy clang-tidy and clang-format for final-wave gate

Suppress clang-analyzer-security buffer-handling diagnostics on the
plan-mandated __builtin_memcpy word loads and bugprone swappable-
parameter diagnostics on the C-standard signatures; wrap the autoconf
substitution tokens in clang-format off/on (the space clang-format wants
before the closing @ would break config.status substitution).

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <[email protected]>

include/vlibc/features.h.in

@@ -22,6 +22,7 @@
  * values baked in at configure time.
  */
 
+/* clang-format off */
 #ifndef VLIBC_LEVEL
 #define VLIBC_LEVEL @vlibc_level@
 #endif
@@ -29,6 +30,7 @@
 #ifndef VLIBC_PROFILE
 #define VLIBC_PROFILE "@vlibc_profile@"
 #endif
+/* clang-format on */
 
 /* True when the active profile is at least level n. */
 #define VLIBC_LEVEL_GE(n) (VLIBC_LEVEL >= (n))