fix: resolve golangci-lint warnings

- Handle ignored errors with explicit _ assignment (errcheck)
- Add #nosec comments for false positive G304/G204 warnings (gosec)
- Fix misspelling: cancelled -> canceled

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/reset/git.go

@@ -72,7 +72,7 @@ func GitRemoveBeads(beadsDir string) error {
 	// Try to remove each file (git rm ignores non-existent files with --ignore-unmatch)
 	// Use --force to handle files with staged changes
 	for _, file := range jsonlFiles {
-		cmd := exec.Command("git", "rm", "--ignore-unmatch", "--quiet", "--force", file)
+		cmd := exec.Command("git", "rm", "--ignore-unmatch", "--quiet", "--force", file) // #nosec G204 -- git is a constant, file is from controlled source
 		var stderr bytes.Buffer
 		cmd.Stderr = &stderr