cleanup: remove dead code (C) + hoist shared TextEncoder (JS)

- C: drop the unreachable fprintf/exit after load_map_from_embedded() (the
  embedded map is the guaranteed fallback; the error path could never run).
- JS: allocate one module-level TextEncoder instead of 'new TextEncoder()' per
  character in the decode passthrough loops (audit dim 6/8).

Author: pmarreck

js/printable_binary.js

@@ -9,6 +9,9 @@
 const isNodeEnv = typeof process !== 'undefined' && !!process.versions?.node;
 const isDenoEnv = typeof Deno !== 'undefined' && typeof Deno.readTextFileSync === 'function';
 
+// A TextEncoder is stateless; share one instead of allocating per character.
+const sharedTextEncoder = new TextEncoder();
+
 const CONTROL_NAMES = [
   'NUL','SOH','STX','ETX','EOT','ENQ','ACK','BEL',
   'BS','TAB','LF','VT','FF','CR','SO','SI',
@@ -363,7 +366,7 @@ class PrintableBinary {
         if (codePoint !== undefined) {
           // Encode the code point to UTF-8 bytes and add to result
           const char = String.fromCodePoint(codePoint);
-          const encoder = new TextEncoder();
+          const encoder = sharedTextEncoder;
           const bytes = encoder.encode(char);
           for (const byte of bytes) {
             result.push(byte);
@@ -550,7 +553,7 @@ class PrintableBinary {
         const codePoint = printableString.codePointAt(i);
         if (codePoint !== undefined) {
           const char = String.fromCodePoint(codePoint);
-          const encoder = new TextEncoder();
+          const encoder = sharedTextEncoder;
           const bytes = encoder.encode(char);
           for (const byte of bytes) {
             result.push(byte);
@@ -622,7 +625,7 @@ class PrintableBinary {
    * @returns {string} The encoded printable string
    */
   encodeString(str, options = {}) {
-    const encoder = new TextEncoder();
+    const encoder = sharedTextEncoder;
     const bytes = encoder.encode(str);
     return this.encode(bytes, options);
   }

src/printable_binary.c

@@ -438,11 +438,9 @@ static void load_character_map(const char *argv0) {
         return;
     }
 
+    /* The embedded map is the guaranteed final fallback (load_map_from_embedded
+     * exits on a malformed embed), so reaching here always succeeds. */
     load_map_from_embedded();
-    return;
-
-    fprintf(stderr, "Error: Unable to load character_map.txt. Set PRINTABLE_BINARY_MAP or place the file alongside the executable.\n");
-    exit(1);
 }
 
 static const char *ascii_name_for_byte(uint8_t value, char *buffer, size_t buffer_size) {