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/ui/ui.go

@@ -4,14 +4,14 @@
 //
 // Message classes (see Writer methods):
 //
-//   - Begin   — operation start, left-aligned, marker "》" (white)
-//   - Complete— operation completion, left-aligned, marker "》" (green)
-//   - Info    — left-aligned neutral status, marker "》" (white)
-//   - Notice  — left-aligned important note, marker "》" (cyan)
-//   - Warning — left-aligned warning, full word "Warning: " (orange/yellow)
-//   - Error   — left-aligned error, full word "ERROR: " (red)
-//   - Progress— indented heartbeat / per-item update, marker "  》" (white)
-//   - Banner  — application banner line, left-aligned, no marker
+//   - Beginf   — operation start, left-aligned, marker "》" (white)
+//   - Completef— operation completion, left-aligned, marker "》" (green)
+//   - Infof    — left-aligned neutral status, marker "》" (white)
+//   - Noticef  — left-aligned important note, marker "》" (cyan)
+//   - Warningf — left-aligned warning, full word "Warning: " (orange/yellow)
+//   - Errorf   — left-aligned error, full word "ERROR: " (red)
+//   - Progressf— indented heartbeat / per-item update, marker "  》" (white)
+//   - Bannerf  — application banner line, left-aligned, no marker
 //
 // Value formatters (Hex, Size, Duration, Time, Path, Snapshot, Speed,
 // Count, Percent) return ANSI-colored strings the caller composes into
@@ -45,6 +45,19 @@ const (
 // Marker is the chevron prefix used for all non-error/warning lines.
 const Marker = "》"
 
+const (
+	// hexAbbrevLen is the number of hash characters Hex keeps before "...".
+	hexAbbrevLen = 12
+
+	// bitsPerByte converts bytes/sec into bits/sec for Speed.
+	bitsPerByte = 8
+
+	// SI thresholds for Speed's unit selection, in bits/sec.
+	gigabit = 1e9
+	megabit = 1e6
+	kilobit = 1e3
+)
+
 // Writer formats and emits user-facing messages with optional ANSI color.
 // It also counts warnings and errors emitted so the caller can summarize at
 // the end of an operation ("Finished successfully." vs "Finished with
@@ -103,15 +116,6 @@ func shouldColor(w io.Writer) bool {
 	return term.IsTerminal(int(f.Fd()))
 }
 
-// paint wraps s in the given ANSI color when color is enabled.
-func (w *Writer) paint(color, s string) string {
-	if !w.color {
-		return s
-	}
-
-	return color + s + ansiReset
-}
-
 // ───────────────────────── message methods ─────────────────────────
 
 // Beginf prints an operation-start line, left-aligned with a white marker.
@@ -208,17 +212,6 @@ func (w *Writer) Bannerf(format string, args ...any) {
 	_, _ = fmt.Fprintln(w.out, body)
 }
 
-// emit writes "<prefix> <body>\n" with the prefix painted in prefixColor
-// and the body optionally painted in bodyColor (empty = no body color).
-func (w *Writer) emit(prefixColor, prefix, bodyColor, format string, args []any) {
-	body := fmt.Sprintf(format, args...)
-	if bodyColor != "" {
-		body = w.paint(bodyColor, body)
-	}
-
-	_, _ = fmt.Fprintln(w.out, w.paint(prefixColor, prefix)+" "+body)
-}
-
 // ───────────────────────── value formatters ─────────────────────────
 //
 // These return ANSI-colored strings the caller composes into a message
@@ -228,8 +221,8 @@ func (w *Writer) emit(prefixColor, prefix, bodyColor, format string, args []any)
 // Long hashes are abbreviated to first 12 chars with "...".
 func (w *Writer) Hex(s string) string {
 	short := s
-	if len(s) > 12 {
-		short = s[:12] + "..."
+	if len(s) > hexAbbrevLen {
+		short = s[:hexAbbrevLen] + "..."
 	}
 
 	return w.paint(ansiCyan, short)
@@ -247,7 +240,7 @@ func (w *Writer) Path(p string) string {
 
 // Size colorizes a byte count using humanize.Bytes.
 func (w *Writer) Size(bytes int64) string {
-	return w.paint(ansiMagenta, humanize.Bytes(uint64(bytes)))
+	return w.paint(ansiMagenta, humanize.Bytes(uint64(bytes))) //nolint:gosec // G115: >=0
 }
 
 // Speed colorizes a network transfer rate. Input is bytes/sec; output is
@@ -258,17 +251,17 @@ func (w *Writer) Speed(bytesPerSec float64) string {
 		return w.paint(ansiMagenta, "N/A")
 	}
 
-	bitsPerSec := bytesPerSec * 8
+	bitsPerSec := bytesPerSec * bitsPerByte
 
 	var s string
 
 	switch {
-	case bitsPerSec >= 1e9:
-		s = fmt.Sprintf("%.1f Gbit/sec", bitsPerSec/1e9)
-	case bitsPerSec >= 1e6:
-		s = fmt.Sprintf("%.0f Mbit/sec", bitsPerSec/1e6)
-	case bitsPerSec >= 1e3:
-		s = fmt.Sprintf("%.0f Kbit/sec", bitsPerSec/1e3)
+	case bitsPerSec >= gigabit:
+		s = fmt.Sprintf("%.1f Gbit/sec", bitsPerSec/gigabit)
+	case bitsPerSec >= megabit:
+		s = fmt.Sprintf("%.0f Mbit/sec", bitsPerSec/megabit)
+	case bitsPerSec >= kilobit:
+		s = fmt.Sprintf("%.0f Kbit/sec", bitsPerSec/kilobit)
 	default:
 		s = fmt.Sprintf("%.0f bit/sec", bitsPerSec)
 	}
@@ -286,7 +279,7 @@ func (w *Writer) Duration(d time.Duration) string {
 // "YYYY-MM-DD HH:MM:SS". No timezone is included — values are
 // displayed in the process's local zone.
 func (w *Writer) Time(t time.Time) string {
-	t = t.Local()
+	t = t.Local() //nolint:gosmopolitan // local-time display is intentional
 
 	now := time.Now()
 	if t.Year() == now.Year() && t.YearDay() == now.YearDay() {
@@ -305,3 +298,25 @@ func (w *Writer) Count(n int) string {
 func (w *Writer) Percent(p float64) string {
 	return w.paint(ansiMagenta, fmt.Sprintf("%.1f%%", p))
 }
+
+// ───────────────────────── internal helpers ─────────────────────────
+
+// paint wraps s in the given ANSI color when color is enabled.
+func (w *Writer) paint(color, s string) string {
+	if !w.color {
+		return s
+	}
+
+	return color + s + ansiReset
+}
+
+// emit writes "<prefix> <body>\n" with the prefix painted in prefixColor
+// and the body optionally painted in bodyColor (empty = no body color).
+func (w *Writer) emit(prefixColor, prefix, bodyColor, format string, args []any) {
+	body := fmt.Sprintf(format, args...)
+	if bodyColor != "" {
+		body = w.paint(bodyColor, body)
+	}
+
+	_, _ = fmt.Fprintln(w.out, w.paint(prefixColor, prefix)+" "+body)
+}