Optimize and simplify loops, table lookups, and branchless parsers

- Replace sequential colon-counting loop with branchless CTZ bitmask in src/pen.h
- Replace linear strchr with 256-bit ASCII punctuation bitmask in src/selection.c
- Flatten 3D color cube loop and precompute constants in src/palette.c
- Use static 256-byte LUT for hex decoding and bsearch for termcap in src/escape.c
- Replace capacity doubling while loops with branchless CLZ pow2 helpers across core
- Use direct memset/memcpy in src/snapshot.c
- Optimize input digit/byte formatting, alt-prefix path, and make keyboard state optional in src/input.c

1 files changed, 9 insertions, 3 deletions

diff --git a/src/pen.h b/src/pen.h
index d7118b5..8349566 100644
--- a/src/pen.h
+++ b/src/pen.h
@@ -1,6 +1,7 @@
 #ifndef WSAP_TERM_PEN_H
 #define WSAP_TERM_PEN_H
 
+#include "compat.h"
 #include "term.h"
 #include <stdbool.h>
 #include <stdint.h>
@@ -78,9 +79,14 @@ static inline int sgr_extended_color(const int *params, int nparams, uint16_t su
     if (params[i + 1] != 2)
         return 0;
     int colon = 0;
-    while (i + 2 + colon < nparams && i + 2 + colon < 16 &&
-           (subparams & (1u << (i + 2 + colon))))
-        colon++;
+    int k = i + 2;
+    if (k < 16 && k < nparams) {
+        uint32_t shifted = (~(uint32_t)subparams) >> k;
+        colon = term_ctz32(shifted);
+        int max_colon = (nparams < 16 ? nparams : 16) - k;
+        if (colon > max_colon)
+            colon = max_colon;
+    }
     int skip = colon >= 4 ? 1 : 0;
     if (i + 4 + skip >= nparams)
         return 0;