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/sheets/filter.go

@@ -2,6 +2,7 @@ package sheets
 
 import (
 	"strings"
+	"unicode/utf8"
 
 	"github.com/cheat/cheat/internal/sheet"
 )
@@ -31,7 +32,8 @@ func Filter(
 			// iterate over each tag. If the sheet does not match *all* tags, filter
 			// it out.
 			for _, tag := range tags {
-				if !sheet.Tagged(strings.TrimSpace(tag)) {
+				trimmed := strings.TrimSpace(tag)
+				if trimmed == "" || !utf8.ValidString(trimmed) || !sheet.Tagged(trimmed) {
 					keep = false
 				}
 			}