Remediate all lint findings under the canonical golangci-lint config

Fix every finding surfaced by the canonical .golangci.yml with
golangci-lint v2.12.2 (refs #61), behavior-preserving throughout:

- err113: dynamic errors replaced with package-level sentinels and %w
  wrapping; direct comparisons converted to errors.Is
- goprintffuncname: printf-style helpers renamed with an f suffix
  (ui.Writer message methods, cli.ReportErrorf, database.Fatalf,
  vaultik stdoutf) and all call sites updated
- revive: stuttering type names renamed (blob.Handler, blob.WithReader,
  blob.ChunkPosition, storage.URL, storage.Info), doc comments added,
  unused parameters blanked, package comments added
- contextcheck/noctx: ctx threaded through blob.Packer
  (AddChunk/Flush/FinalizeBlob/PackChunks) and scanner call sites;
  context-aware exec and sql variants used
- funlen/cyclop/gocognit/nestif/dupl: oversized or duplicated
  functions split into focused helpers across production and test code
- paralleltest/tparallel/thelper/usetesting/testpackage: tests
  parallelized where safe (global log.Initialize kept in the serial
  phase), helpers marked, t.TempDir adopted, external test packages
  where only exported API is used
- gosec: integer conversions clamped or justified, header timeouts
  added, remaining findings suppressed with per-site justifications
- mnd/goconst/lll/wsl_v5/nlreturn/noinlineerr/errcheck and other
  mechanical findings fixed directly

Remove the deprecated log.LogOptions alias (callers migrated to
log.Options). make check is green.

internal/pidlock/pidlock.go

@@ -21,6 +21,13 @@ type Lock struct {
 	path string
 }
 
+const (
+	// lockDirPerm is the mode for the lock directory (owner-only).
+	lockDirPerm = 0o700
+	// pidFilePerm is the mode for the PID file (owner-only).
+	pidFilePerm = 0o600
+)
+
 // Acquire attempts to acquire a PID lock in the specified directory.
 // If the lock file exists and the process is still running, it returns
 // ErrAlreadyRunning with details about the existing process.
@@ -28,7 +35,8 @@ type Lock struct {
 // a Lock that must be released with Release().
 func Acquire(lockDir string) (*Lock, error) {
 	// Ensure lock directory exists
-	if err := os.MkdirAll(lockDir, 0700); err != nil {
+	err := os.MkdirAll(lockDir, lockDirPerm)
+	if err != nil {
 		return nil, fmt.Errorf("creating lock directory: %w", err)
 	}
 
@@ -46,7 +54,9 @@ func Acquire(lockDir string) (*Lock, error) {
 
 	// Write our PID
 	pid := os.Getpid()
-	if err := os.WriteFile(lockPath, []byte(strconv.Itoa(pid)), 0600); err != nil {
+
+	err = os.WriteFile(lockPath, []byte(strconv.Itoa(pid)), pidFilePerm)
+	if err != nil {
 		return nil, fmt.Errorf("writing PID file: %w", err)
 	}
 
@@ -64,7 +74,7 @@ func (l *Lock) Release() error {
 	existingPID, err := readPIDFile(l.path)
 	if err != nil {
 		// File already gone or unreadable - that's fine
-		return nil
+		return nil //nolint:nilerr // unreadable lock file means nothing to release
 	}
 
 	if existingPID != os.Getpid() {
@@ -72,7 +82,8 @@ func (l *Lock) Release() error {
 		return nil
 	}
 
-	if err := os.Remove(l.path); err != nil && !os.IsNotExist(err) {
+	err = os.Remove(l.path)
+	if err != nil && !os.IsNotExist(err) {
 		return fmt.Errorf("removing PID file: %w", err)
 	}
 
@@ -83,7 +94,7 @@ func (l *Lock) Release() error {
 
 // readPIDFile reads and parses the PID from a lock file.
 func readPIDFile(path string) (int, error) {
-	data, err := os.ReadFile(path)
+	data, err := os.ReadFile(path) //nolint:gosec // G304: path is our own lock file
 	if err != nil {
 		return 0, err
 	}