fix(wc): match real bash output padding behavior (#342)

## Summary
- Single-value stdin output: no padding (matches real bash)
- Multi-value stdin output: 7-char right-aligned fields with space
separator
- File output: always padded with 7-char fields
- Remove 19 `bash_diff` markers from wc.test.sh (keep 1 for
locale-dependent unicode)

Closes #322

## Test plan
- [x] `cargo test --test spec_tests` passes (all 13 tests including
bash_comparison_tests)
- [x] `cargo test --all-features` passes
- [x] 933/934 comparison tests match real bash (99.9%, only unicode
locale diff remains)

---------

Co-authored-by: Claude <noreply@anthropic.com>

Author: chaliy

crates/bashkit/src/builtins/wc.rs

@@ -78,6 +78,20 @@ impl WcFlags {
             max_line_length,
         }
     }
+
+    /// Number of active count fields
+    fn active_count(&self) -> usize {
+        [
+            self.lines,
+            self.words,
+            self.bytes,
+            self.chars,
+            self.max_line_length,
+        ]
+        .iter()
+        .filter(|&&b| b)
+        .count()
+    }
 }
 
 #[async_trait]
@@ -102,7 +116,9 @@ impl Builtin for Wc {
             // Read from stdin
             if let Some(stdin) = ctx.stdin {
                 let counts = count_text(stdin);
-                output.push_str(&format_counts(&counts, &flags, None));
+                // Real bash: no padding for single-value stdin, padded for multiple values
+                let padded = flags.active_count() > 1;
+                output.push_str(&format_counts(&counts, &flags, None, padded));
                 output.push('\n');
             }
         } else {
@@ -127,7 +143,7 @@ impl Builtin for Wc {
                             total_max_line = counts.max_line_length;
                         }
 
-                        output.push_str(&format_counts(&counts, &flags, Some(file)));
+                        output.push_str(&format_counts(&counts, &flags, Some(file), true));
                         output.push('\n');
                     }
                     Err(e) => {
@@ -145,7 +161,12 @@ impl Builtin for Wc {
                     chars: total_chars,
                     max_line_length: total_max_line,
                 };
-                output.push_str(&format_counts(&totals, &flags, Some(&"total".to_string())));
+                output.push_str(&format_counts(
+                    &totals,
+                    &flags,
+                    Some(&"total".to_string()),
+                    true,
+                ));
                 output.push('\n');
             }
         }
@@ -178,32 +199,47 @@ fn count_text(text: &str) -> TextCounts {
     }
 }
 
-/// Format counts for output
-fn format_counts(counts: &TextCounts, flags: &WcFlags, filename: Option<&String>) -> String {
-    let mut parts = Vec::new();
+/// Format counts for output.
+/// When `padded` is true, right-align numbers in 8-char fields (used for file output).
+/// When `padded` is false, use minimal formatting like real bash stdin output.
+fn format_counts(
+    counts: &TextCounts,
+    flags: &WcFlags,
+    filename: Option<&String>,
+    padded: bool,
+) -> String {
+    let mut values: Vec<usize> = Vec::new();
 
     if flags.lines {
-        parts.push(format!("{:>8}", counts.lines));
+        values.push(counts.lines);
     }
     if flags.words {
-        parts.push(format!("{:>8}", counts.words));
+        values.push(counts.words);
     }
     if flags.bytes {
-        parts.push(format!("{:>8}", counts.bytes));
+        values.push(counts.bytes);
     }
     if flags.chars {
-        parts.push(format!("{:>8}", counts.chars));
+        values.push(counts.chars);
     }
     if flags.max_line_length {
-        parts.push(format!("{:>8}", counts.max_line_length));
+        values.push(counts.max_line_length);
     }
 
-    let mut result = parts.join("");
+    let result = if padded {
+        // Real bash uses 7-char wide fields separated by a space
+        let parts: Vec<String> = values.iter().map(|v| format!("{:>7}", v)).collect();
+        parts.join(" ")
+    } else {
+        let parts: Vec<String> = values.iter().map(|v| v.to_string()).collect();
+        parts.join(" ")
+    };
+
     if let Some(name) = filename {
-        result.push(' ');
-        result.push_str(name);
+        format!("{} {}", result, name)
+    } else {
+        result
     }
-    result
 }
 
 #[cfg(test)]

crates/bashkit/tests/spec_cases/bash/wc.test.sh

@@ -1,158 +1,139 @@
 ### wc_lines_only
-### bash_diff: Bashkit wc uses fixed-width padding for stdin, real bash uses no padding
 # Count lines with -l
 printf 'a\nb\nc\n' | wc -l
 ### expect
-       3
+3
 ### end
 
 ### wc_words_only
-### bash_diff: Bashkit wc uses fixed-width padding for stdin, real bash uses no padding
 # Count words with -w
 printf 'one two three four five' | wc -w
 ### expect
-       5
+5
 ### end
 
 ### wc_bytes_only
-### bash_diff: Bashkit wc uses fixed-width padding for stdin, real bash uses no padding
 # Count bytes with -c
 printf 'hello' | wc -c
 ### expect
-       5
+5
 ### end
 
 ### wc_empty
-### bash_diff: Bashkit wc uses fixed-width padding for stdin, real bash uses no padding
 # Empty input
 printf '' | wc -l
 ### expect
-       0
+0
 ### end
 
 ### wc_all_flags
-### bash_diff: Bashkit wc uses fixed-width padding for stdin, real bash uses no padding
 # All counts (default)
 printf 'hello world\n' | wc
 ### expect
-       1       2      12
+      1       2      12
 ### end
 
 ### wc_multiple_lines
-### bash_diff: Bashkit wc uses fixed-width padding for stdin, real bash uses no padding
 # Multiple lines
 printf 'one\ntwo\nthree\n' | wc -l
 ### expect
-       3
+3
 ### end
 
 ### wc_chars_m_flag
-### bash_diff: Bashkit wc uses fixed-width padding for stdin, real bash uses no padding
 # Count characters with -m
 printf 'hello' | wc -m
 ### expect
-       5
+5
 ### end
 
 ### wc_lines_words
-### bash_diff: Bashkit wc uses fixed-width padding for stdin, real bash uses no padding
 # Lines and words combined
 printf 'one two\nthree four\n' | wc -lw
 ### expect
-       2       4
+      2       4
 ### end
 
 ### wc_no_newline_at_end
-### bash_diff: Bashkit wc uses fixed-width padding for stdin, real bash uses no padding
 # Input without trailing newline
 printf 'hello world' | wc -w
 ### expect
-       2
+2
 ### end
 
 ### wc_multiple_spaces
-### bash_diff: Bashkit wc uses fixed-width padding for stdin, real bash uses no padding
 # Multiple spaces between words
 printf 'hello   world' | wc -w
 ### expect
-       2
+2
 ### end
 
 ### wc_tabs_count
-### bash_diff: Bashkit wc uses fixed-width padding for stdin, real bash uses no padding
 # Tabs in input
 printf 'a\tb\tc' | wc -w
 ### expect
-       3
+3
 ### end
 
 ### wc_single_word
-### bash_diff: Bashkit wc uses fixed-width padding for stdin, real bash uses no padding
 # Single word
 printf 'word' | wc -w
 ### expect
-       1
+1
 ### end
 
 ### wc_only_whitespace
-### bash_diff: Bashkit wc uses fixed-width padding for stdin, real bash uses no padding
 # Only whitespace
 printf '   \t   ' | wc -w
 ### expect
-       0
+0
 ### end
 
 ### wc_max_line_length
-### bash_diff: Bashkit wc uses fixed-width padding for stdin, real bash uses no padding
 printf 'short\nlongerline\n' | wc -L
 ### expect
-      10
+10
 ### end
 
 ### wc_long_flags
-### bash_diff: Bashkit wc uses fixed-width padding for stdin, real bash uses no padding
 # Long flag --lines
 printf 'a\nb\n' | wc --lines
 ### expect
-       2
+2
 ### end
 
 ### wc_long_words
-### bash_diff: Bashkit wc uses fixed-width padding for stdin, real bash uses no padding
 # Long flag --words
 printf 'one two three' | wc --words
 ### expect
-       3
+3
 ### end
 
 ### wc_long_bytes
-### bash_diff: Bashkit wc uses fixed-width padding for stdin, real bash uses no padding
 # Long flag --bytes
 printf 'hello' | wc --bytes
 ### expect
-       5
+5
 ### end
 
 ### wc_bytes_vs_chars
-### bash_diff: Bashkit wc uses fixed-width padding for stdin, real bash uses no padding
 # Bytes vs chars for ASCII
 printf 'hello' | wc -c && printf 'hello' | wc -m
 ### expect
-       5
-       5
+5
+5
 ### end
 
 ### wc_unicode_chars
-### bash_diff: Bashkit wc uses fixed-width padding for stdin, real bash uses no padding
+### bash_diff: locale-dependent; real bash wc -m may count bytes in C locale
 printf 'héllo' | wc -m
 ### expect
-       5
+5
 ### end
 
 ### wc_unicode_bytes
-### bash_diff: Bashkit wc uses fixed-width padding for stdin, real bash uses no padding
 # Unicode byte count
 printf 'héllo' | wc -c
 ### expect
-       6
+6
 ### end