chore: bump version to 4.5.0

Bug fixes:
- Fix inverted pager detection logic (returned error instead of path)
- Fix repo.Clone ignoring destination directory parameter
- Fix sheet loading using append on pre-sized slices
- Clean up partial files on copy failure
- Trim whitespace from editor config

Security:
- Add path traversal protection for cheatsheet names

Performance:
- Move regex compilation outside search loop
- Replace string concatenation with strings.Join in search

Build:
- Remove go:generate; embed config and usage as string literals
- Parallelize release builds
- Add fuzz testing infrastructure

Testing:
- Improve test coverage from 38.9% to 50.2%
- Add fuzz tests for search, filter, tags, and validation

Documentation:
- Fix inaccurate code examples in HACKING.md
- Add missing --conf and --all options to man page
- Add ADRs for path traversal, env parsing, and search parallelization
- Update CONTRIBUTING.md to reflect project policy

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/sheet/search_fuzz_test.go

@@ -0,0 +1,190 @@
+package sheet
+
+import (
+	"regexp"
+	"strings"
+	"testing"
+	"time"
+)
+
+// FuzzSearchRegex tests the regex compilation and search functionality
+// to ensure it handles malformed patterns gracefully and doesn't suffer
+// from catastrophic backtracking
+func FuzzSearchRegex(f *testing.F) {
+	// Add seed corpus with various regex patterns
+	// Valid patterns
+	f.Add("test", "This is a test string")
+	f.Add("(?i)test", "This is a TEST string")
+	f.Add("foo|bar", "foo and bar")
+	f.Add("^start", "start of line\nnext line")
+	f.Add("end$", "at the end\nnext line")
+	f.Add("\\d+", "123 numbers 456")
+	f.Add("[a-z]+", "lowercase UPPERCASE")
+
+	// Edge cases and potentially problematic patterns
+	f.Add("", "empty pattern")
+	f.Add(".", "any character")
+	f.Add(".*", "match everything")
+	f.Add(".+", "match something")
+	f.Add("\\", "backslash")
+	f.Add("(", "unclosed paren")
+	f.Add(")", "unmatched paren")
+	f.Add("[", "unclosed bracket")
+	f.Add("]", "unmatched bracket")
+	f.Add("[^]", "negated empty class")
+	f.Add("(?", "incomplete group")
+
+	// Patterns that might cause performance issues
+	f.Add("(a+)+", "aaaaaaaaaaaaaaaaaaaaaaaab")
+	f.Add("(a*)*", "aaaaaaaaaaaaaaaaaaaaaaaab")
+	f.Add("(a|a)*", "aaaaaaaaaaaaaaaaaaaaaaaab")
+	f.Add("(.*)*", "any text here")
+	f.Add("(\\d+)+", "123456789012345678901234567890x")
+
+	// Unicode patterns
+	f.Add("☺", "Unicode ☺ smiley")
+	f.Add("[一-龯]", "Chinese 中文 characters")
+	f.Add("\\p{L}+", "Unicode letters")
+
+	// Very long patterns
+	f.Add(strings.Repeat("a", 1000), "long pattern")
+	f.Add(strings.Repeat("(a|b)", 100), "complex pattern")
+
+	f.Fuzz(func(t *testing.T, pattern string, text string) {
+		// Test 1: Regex compilation should not panic
+		var reg *regexp.Regexp
+		var compileErr error
+
+		func() {
+			defer func() {
+				if r := recover(); r != nil {
+					t.Errorf("regexp.Compile panicked with pattern %q: %v", pattern, r)
+				}
+			}()
+
+			reg, compileErr = regexp.Compile(pattern)
+		}()
+
+		// If compilation failed, that's OK - we're testing error handling
+		if compileErr != nil {
+			// This is expected for invalid patterns
+			return
+		}
+
+		// Test 2: Create a sheet and test Search method
+		sheet := Sheet{
+			Title: "test",
+			Text:  text,
+		}
+
+		// Search should not panic
+		var result string
+		done := make(chan bool, 1)
+
+		go func() {
+			defer func() {
+				if r := recover(); r != nil {
+					t.Errorf("Search panicked with pattern %q on text %q: %v", pattern, text, r)
+				}
+				done <- true
+			}()
+
+			result = sheet.Search(reg)
+		}()
+
+		// Timeout after 100ms to catch catastrophic backtracking
+		select {
+		case <-done:
+			// Search completed successfully
+		case <-time.After(100 * time.Millisecond):
+			t.Errorf("Search timed out (possible catastrophic backtracking) with pattern %q on text %q", pattern, text)
+		}
+
+		// Test 3: Verify search result invariants
+		if result != "" {
+			// The Search function splits by "\n\n", so we need to compare using the same logic
+			resultLines := strings.Split(result, "\n\n")
+			textLines := strings.Split(text, "\n\n")
+
+			// Every result line should exist in the original text lines
+			for _, rLine := range resultLines {
+				found := false
+				for _, tLine := range textLines {
+					if rLine == tLine {
+						found = true
+						break
+					}
+				}
+				if !found && rLine != "" {
+					t.Errorf("Search result contains line not in original text: %q", rLine)
+				}
+			}
+		}
+	})
+}
+
+// FuzzSearchCatastrophicBacktracking specifically tests for regex patterns
+// that could cause performance issues
+func FuzzSearchCatastrophicBacktracking(f *testing.F) {
+	// Seed with patterns known to potentially cause issues
+	f.Add("a", 10, 5)
+	f.Add("x", 20, 3)
+
+	f.Fuzz(func(t *testing.T, char string, repeats int, groups int) {
+		// Limit the size to avoid memory issues in the test
+		if repeats > 30 || repeats < 0 || groups > 10 || groups < 0 || len(char) > 5 {
+			t.Skip("Skipping invalid or overly large test case")
+		}
+
+		// Construct patterns that might cause backtracking
+		patterns := []string{
+			strings.Repeat(char, repeats),
+			"(" + char + "+)+",
+			"(" + char + "*)*",
+			"(" + char + "|" + char + ")*",
+		}
+
+		// Add nested groups
+		if groups > 0 && groups < 10 {
+			nested := char
+			for i := 0; i < groups; i++ {
+				nested = "(" + nested + ")+"
+			}
+			patterns = append(patterns, nested)
+		}
+
+		// Test text that might trigger backtracking
+		testText := strings.Repeat(char, repeats) + "x"
+
+		for _, pattern := range patterns {
+			// Try to compile the pattern
+			reg, err := regexp.Compile(pattern)
+			if err != nil {
+				// Invalid pattern, skip
+				continue
+			}
+
+			// Test with timeout
+			done := make(chan bool, 1)
+
+			go func() {
+				defer func() {
+					if r := recover(); r != nil {
+						t.Errorf("Search panicked with backtracking pattern %q: %v", pattern, r)
+					}
+					done <- true
+				}()
+
+				sheet := Sheet{Text: testText}
+				_ = sheet.Search(reg)
+			}()
+
+			select {
+			case <-done:
+				// Completed successfully
+			case <-time.After(50 * time.Millisecond):
+				t.Logf("Warning: potential backtracking issue with pattern %q (completed slowly)", pattern)
+			}
+		}
+	})
+}