Enable errcheck linter and fix all production code warnings

- Enabled errcheck linter (previously disabled)
- Set tests: false in .golangci.yml to focus on production code
- Fixed 27 errcheck warnings using Go best practices:
  * Database resources: defer func() { _ = rows.Close() }()
  * Transaction rollbacks: defer func() { _ = tx.Rollback() }()
  * Best-effort closers: _ = store.Close(), _ = client.Close()
  * File writes: proper error checking on Close()
  * Interactive input: handle EOF gracefully
  * File ops: ignore ENOENT on os.Remove()
- All tests pass
- Closes bd-58

Amp-Thread-ID: https://ampcode.com/threads/T-57c9afd3-9adf-40c2-8be7-3e493d200361
Co-authored-by: Amp <amp@ampcode.com>

cmd/bd/delete.go

@@ -606,7 +606,7 @@ func readIssueIDsFromFile(filename string) ([]string, error) {
 	if err != nil {
 		return nil, err
 	}
-	defer f.Close()
+	defer func() { _ = f.Close() }()
 
 	var ids []string
 	scanner := bufio.NewScanner(f)

cmd/bd/dep.go

@@ -174,7 +174,7 @@ var depTreeCmd = &cobra.Command{
 				fmt.Fprintf(os.Stderr, "Error: failed to open database: %v\n", err)
 				os.Exit(1)
 			}
-			defer store.Close()
+			defer func() { _ = store.Close() }()
 		}
 
 		showAllPaths, _ := cmd.Flags().GetBool("show-all-paths")
@@ -245,7 +245,7 @@ var depCyclesCmd = &cobra.Command{
 				fmt.Fprintf(os.Stderr, "Error: failed to open database: %v\n", err)
 				os.Exit(1)
 			}
-			defer store.Close()
+			defer func() { _ = store.Close() }()
 		}
 
 		ctx := context.Background()

cmd/bd/export.go

@@ -20,7 +20,11 @@ func countIssuesInJSONL(path string) (int, error) {
 	if err != nil {
 		return 0, err
 	}
-	defer file.Close()
+	defer func() {
+		if err := file.Close(); err != nil {
+			fmt.Fprintf(os.Stderr, "Warning: failed to close file: %v\n", err)
+		}
+	}()
 
 	count := 0
 	decoder := json.NewDecoder(file)
@@ -100,13 +104,13 @@ Output to stdout by default, or use -o flag for file output.`,
 			}
 			store, err = sqlite.New(dbPath)
 			if err != nil {
-				fmt.Fprintf(os.Stderr, "Error: failed to open database: %v\n", err)
-				os.Exit(1)
+			fmt.Fprintf(os.Stderr, "Error: failed to open database: %v\n", err)
+			os.Exit(1)
+			}
+			defer func() { _ = store.Close() }()
 			}
-			defer store.Close()
-		}
 
-		// Build filter
+			// Build filter
 		filter := types.IssueFilter{}
 		if statusFilter != "" {
 			status := types.Status(statusFilter)
@@ -153,7 +157,7 @@ Output to stdout by default, or use -o flag for file output.`,
 					fmt.Fprintf(os.Stderr, "Press Ctrl+C to abort, or Enter to continue: ")
 					// Read a line from stdin to wait for user confirmation
 					var response string
-					fmt.Scanln(&response)
+					_, _ = fmt.Scanln(&response) // ignore EOF on empty input
 				}
 			}
 		}

cmd/bd/init.go

@@ -178,7 +178,7 @@ if quiet {
 		// Prompt to install
 		fmt.Printf("Install git hooks now? [Y/n] ")
 		var response string
-		fmt.Scanln(&response)
+		_, _ = fmt.Scanln(&response) // ignore EOF on empty input
 		response = strings.ToLower(strings.TrimSpace(response))
 		
 		if response == "" || response == "y" || response == "yes" {

cmd/bd/main.go

@@ -587,7 +587,7 @@ func restartDaemonForVersionMismatch() bool {
 		cmd.Stdin = devNull
 		cmd.Stdout = devNull
 		cmd.Stderr = devNull
-		defer devNull.Close()
+		defer func() { _ = devNull.Close() }()
 	}
 
 	if err := cmd.Start(); err != nil {
@@ -637,7 +637,11 @@ func tryAutoStartDaemon(socketPath string) bool {
 	if !acquireStartLock(lockPath, socketPath) {
 		return false
 	}
-	defer os.Remove(lockPath)
+	defer func() {
+		if err := os.Remove(lockPath); err != nil && !os.IsNotExist(err) {
+			debugLog("failed to remove lock file: %v", err)
+		}
+	}()
 
 	if handleExistingSocket(socketPath) {
 		return true
@@ -777,7 +781,7 @@ func setupDaemonIO(cmd *exec.Cmd) {
 		cmd.Stdin = devNull
 		go func() {
 			time.Sleep(1 * time.Second)
-			devNull.Close()
+			_ = devNull.Close()
 		}()
 	}
 }

cmd/bd/ready.go

@@ -148,13 +148,13 @@ var blockedCmd = &cobra.Command{
 			var err error
 			store, err = sqlite.New(dbPath)
 			if err != nil {
-				fmt.Fprintf(os.Stderr, "Error: failed to open database: %v\n", err)
-				os.Exit(1)
+			fmt.Fprintf(os.Stderr, "Error: failed to open database: %v\n", err)
+			os.Exit(1)
+			}
+			defer func() { _ = store.Close() }()
 			}
-			defer store.Close()
-		}
 
-		ctx := context.Background()
+			ctx := context.Background()
 		blocked, err := store.GetBlockedIssues(ctx)
 		if err != nil {
 			fmt.Fprintf(os.Stderr, "Error: %v\n", err)

cmd/bd/renumber.go

@@ -55,13 +55,13 @@ Risks:
 			}
 			store, err = sqlite.New(dbPath)
 			if err != nil {
-				fmt.Fprintf(os.Stderr, "Error: failed to open database: %v\n", err)
-				os.Exit(1)
+			fmt.Fprintf(os.Stderr, "Error: failed to open database: %v\n", err)
+			os.Exit(1)
+			}
+			defer func() { _ = store.Close() }()
 			}
-			defer store.Close()
-		}
 
-		ctx := context.Background()
+			ctx := context.Background()
 
 		// Get prefix from config, or derive from first issue if not set
 		prefix, err := store.GetConfig(ctx, "issue_prefix")

cmd/bd/restore.go

@@ -158,7 +158,7 @@ func readIssueFromJSONL(jsonlPath, issueID string) (*types.Issue, error) {
 	if err != nil {
 		return nil, fmt.Errorf("failed to open JSONL: %w", err)
 	}
-	defer file.Close()
+	defer func() { _ = file.Close() }()
 
 	scanner := bufio.NewScanner(file)
 	// Increase buffer size for large issues

cmd/bd/stale.go

@@ -153,7 +153,7 @@ func getStaleIssues(thresholdSeconds int) ([]*StaleIssueInfo, error) {
 	if err != nil {
 		return nil, fmt.Errorf("failed to query stale issues: %w", err)
 	}
-	defer rows.Close()
+	defer func() { _ = rows.Close() }()
 
 	var staleIssues []*StaleIssueInfo
 	for rows.Next() {
@@ -221,7 +221,7 @@ func releaseStaleIssues(staleIssues []*StaleIssueInfo) (int, error) {
 	if err != nil {
 		return 0, fmt.Errorf("failed to begin transaction: %w", err)
 	}
-	defer tx.Rollback()
+	defer func() { _ = tx.Rollback() }()
 
 	releaseCount := 0
 	now := time.Now()

cmd/bd/version.go

@@ -55,7 +55,7 @@ func showDaemonVersion() {
 		fmt.Fprintf(os.Stderr, "Hint: start daemon with 'bd daemon'\n")
 		os.Exit(1)
 	}
-	defer client.Close()
+	defer func() { _ = client.Close() }()
 
 	health, err := client.Health()
 	if err != nil {