feat(tui): stumble mode — resurface stale entries card by card

Card-by-card walkthrough of entries untouched for 30+ days.
Prevents write-mostly decay by bringing old entries back to attention.

- S from list triggers stumble, loads entries where modified_at < 30d
- Single-card view with markdown body, glyph, tags, age indicator
- Actions: n skip, d dismiss, ! pin, p promote, m absorb, esc exit
- Progress indicator: stumble [3/12]
- After promote/absorb from stumble, returns to deck (not list)
- "All caught up" screen when deck exhausted
- DB: add ModifiedBefore to ListParams, modified_at sort column

internal/tui/stumble.go

@@ -0,0 +1,164 @@
+package tui
+
+import (
+	"fmt"
+	"math"
+	"strings"
+	"time"
+
+	"github.com/charmbracelet/glamour"
+
+	"github.com/lerko/nib/internal/db"
+	"github.com/lerko/nib/internal/display"
+)
+
+const staleThresholdDays = 30
+
+type stumbleModel struct {
+	entries []*db.Entity
+	cursor  int
+	width   int
+	height  int
+	done    bool
+}
+
+func newStumbleModel() stumbleModel {
+	return stumbleModel{}
+}
+
+func (s *stumbleModel) setEntries(entries []*db.Entity) {
+	s.entries = entries
+	s.cursor = 0
+	s.done = len(entries) == 0
+}
+
+func (s *stumbleModel) setSize(width, height int) {
+	s.width = width
+	s.height = height
+}
+
+func (s stumbleModel) current() *db.Entity {
+	if s.done || len(s.entries) == 0 || s.cursor >= len(s.entries) {
+		return nil
+	}
+	return s.entries[s.cursor]
+}
+
+func (s *stumbleModel) advance() {
+	s.cursor++
+	if s.cursor >= len(s.entries) {
+		s.done = true
+	}
+}
+
+func (s *stumbleModel) removeCurrent() {
+	if s.cursor < len(s.entries) {
+		s.entries = append(s.entries[:s.cursor], s.entries[s.cursor+1:]...)
+		if s.cursor >= len(s.entries) {
+			s.done = true
+		}
+	}
+}
+
+func (s stumbleModel) total() int {
+	return len(s.entries)
+}
+
+func (s stumbleModel) view() string {
+	if s.done {
+		return s.doneView()
+	}
+
+	e := s.current()
+	if e == nil {
+		return s.doneView()
+	}
+
+	w := s.width
+	var b strings.Builder
+
+	progress := fmt.Sprintf("stumble [%d/%d]", s.cursor+1, len(s.entries))
+	b.WriteString(detailHeaderStyle.Render(progress))
+	b.WriteString("\n")
+	b.WriteString(separatorStyle.Render(strings.Repeat("─", w)))
+	b.WriteString("\n\n")
+
+	glyph := display.DisplayGlyph(e.Glyph, e.CardType)
+	title := e.Body
+	if e.Title != nil {
+		title = *e.Title
+	}
+	if len(title) > w-6 {
+		title = title[:w-9] + "…"
+	}
+	b.WriteString("  " + glyphStyle.Render(glyph) + " " + title)
+	b.WriteString("\n")
+
+	var meta []string
+	meta = append(meta, string(e.Glyph))
+	if e.CardType != nil {
+		meta = append(meta, string(*e.CardType))
+	}
+	for _, t := range e.Tags {
+		meta = append(meta, tagStyle.Render("#"+t))
+	}
+	meta = append(meta, "captured "+e.CreatedAt.Format("Jan 2"))
+	b.WriteString("  " + idStyle.Render(strings.Join(meta, " · ")))
+	b.WriteString("\n\n")
+
+	bodyWidth := w - 6
+	if bodyWidth < 20 {
+		bodyWidth = 20
+	}
+	r, _ := glamour.NewTermRenderer(
+		glamour.WithStylePath("dark"),
+		glamour.WithWordWrap(bodyWidth),
+	)
+	rendered, err := r.Render(e.Body)
+	if err != nil {
+		rendered = e.Body
+	}
+	rendered = strings.TrimRight(rendered, "\n")
+	b.WriteString("  " + rendered)
+	b.WriteString("\n\n")
+
+	age := daysAgo(e.ModifiedAt)
+	ageText := fmt.Sprintf("last touched %d days ago", age)
+	b.WriteString("  " + stumbleAgeStyle.Render(ageText))
+	b.WriteString("\n")
+	b.WriteString(separatorStyle.Render(strings.Repeat("─", w)))
+
+	lines := strings.Split(b.String(), "\n")
+	if len(lines) > s.height {
+		lines = lines[:s.height]
+	}
+	return strings.Join(lines, "\n")
+}
+
+func (s stumbleModel) doneView() string {
+	var b strings.Builder
+	b.WriteString("\n\n")
+	b.WriteString(detailHeaderStyle.Render("  all caught up"))
+	b.WriteString("\n\n")
+	reviewed := s.total()
+	if reviewed > 0 {
+		b.WriteString(idStyle.Render(fmt.Sprintf("  %d entries reviewed", reviewed)))
+	} else {
+		b.WriteString(idStyle.Render("  no stale entries found"))
+	}
+	return b.String()
+}
+
+func daysAgo(t time.Time) int {
+	return int(math.Floor(time.Since(t).Hours() / 24))
+}
+
+func staleParams() db.ListParams {
+	threshold := time.Now().UTC().AddDate(0, 0, -staleThresholdDays)
+	return db.ListParams{
+		ModifiedBefore: &threshold,
+		Sort:           "modified_at",
+		Order:          "asc",
+		Limit:          50,
+	}
+}