fix: -p/-P flag consistency (CRITICAL) + JS module type

CRITICAL: Lua had -p = --preserve <chars> (needs arg) and no -P, while
C/Zig/FFI/Node use -p = --passthrough (no arg) and -P = --preserve. Same
command line did opposite things or errored depending on the binary. Lua now
matches the 4-impl majority: -p = passthrough, -P = preserve. Also accept the
--preserve=chars attached form (the other four already do).

JS: add package.json with "type": "module" so Node 24 stops emitting the
MODULE_TYPELESS_PACKAGE_JSON warning to stderr (which broke the stderr-purity
test). All four impls now pass test/test including new cross-impl test #5d
(-p passthrough / -P preserve).

Author: pmarreck

bin/printable-binary

@@ -522,7 +522,7 @@ if arg then
     io.stderr:write("Usage: " .. progname .. " [options] [file]\n")
     io.stderr:write("Options:\n")
     io.stderr:write("  -d, --decode     Decode mode (default is encode mode)\n")
-    io.stderr:write("  --passthrough    Pass input to stdout unchanged, send encoded data to stderr\n")
+    io.stderr:write("  -p, --passthrough                  Pass input to stdout unchanged, send encoded data to stderr\n")
     io.stderr:write("\n")
     io.stderr:write("Encoding modes:\n")
     io.stderr:write("  -X, --hexlike    Hexlike mode: passthrough ASCII stays as-is, all other bytes\n")
@@ -535,7 +535,7 @@ if arg then
     io.stderr:write("  -t, --tabs, --preserve-tabs        Preserve literal tabs\n")
     io.stderr:write("  -n, --crlf, --preserve-newlines    Preserve literal CR/LF\n")
     io.stderr:write("  -w, --preserve-whitespace          Preserve all whitespace (spaces, tabs, CR/LF)\n")
-    io.stderr:write("  -p, --preserve <chars>             Preserve specific characters (e.g., -p '!\"')\n")
+    io.stderr:write("  -P, --preserve <chars>             Preserve specific characters (e.g., -P '!\"')\n")
     io.stderr:write("  --no-double-encode-check           Skip detection of already-encoded input\n")
     io.stderr:write("\n")
     io.stderr:write("Range options (select byte range from input before processing):\n")
@@ -726,9 +726,11 @@ if arg then
     elseif flag == "S" then
       strip_whitespace = true
     elseif flag == "p" then
+      passthrough_mode = true
+    elseif flag == "P" then
       local next_arg = get_next_arg()
       if not next_arg then
-        io.stderr:write("Error: -p requires an argument\n")
+        io.stderr:write("Error: -P requires an argument\n")
         os.exit(1)
       end
       preserve_chars = next_arg
@@ -803,6 +805,8 @@ if arg then
         io.stderr:write("Error: --end value must be a number\n")
         os.exit(1)
       end
+    elseif current_arg:match("^%-%-preserve=") then
+      preserve_chars = current_arg:match("^%-%-preserve=(.*)")
     elseif current_arg == "--preserve" then
       i = i + 1
       if not arg[i] then

package.json

@@ -0,0 +1,12 @@
+{
+  "name": "printable-binary",
+  "version": "1.0.0",
+  "description": "Encode arbitrary binary data into human-readable UTF-8 and back (Node/ESM implementation).",
+  "type": "module",
+  "private": true,
+  "bin": {
+    "printable-binary-node": "bin/printable-binary-node.js"
+  },
+  "main": "js/printable_binary.js",
+  "license": "MIT"
+}

test/test

@@ -253,6 +253,17 @@ else
     echo -e "${YELLOW}SKIP (no character_map.txt in cwd)${NC}"
 fi
 
+# Test 5d: -p (passthrough) / -P (preserve) short-flag consistency across all impls
+echo -e "${BLUE}Test #5d: -p passthrough / -P preserve consistency${NC}"
+PT=$(printf 'hi' | $SCRIPT -p 2>/dev/null)
+PR=$(printf '!' | $SCRIPT -P '!' 2>/dev/null)
+if [[ "$PT" == "hi" && "$PR" == "!" ]]; then
+    echo -e "${GREEN}PASS${NC}"
+else
+    echo -e "${RED}FAIL${NC} (-p passthrough='$PT' want 'hi'; -P preserve='$PR' want '!')"
+    exit 1
+fi
+
 # Test 6: Piped input
 echo -e "${BLUE}Test #6: Piped input${NC}"
 RESULT=$(echo -n "Test" | $SCRIPT | $SCRIPT -d)