feat(tui): add search via capture bar and absorb flow

Search uses existing parse grammar ?prefix — type `?query #tag` in
capture bar to filter entities client-side. Substring match on
body+title+description with AND tag filtering. Esc clears search.

Absorb via m key on fluid entities — opens source picker showing all
other entities, enter merges source into target. Uses existing
store.Absorb() backend.

internal/tui/absorb.go

@@ -0,0 +1,136 @@
+package tui
+
+import (
+	"fmt"
+	"strings"
+
+	tea "github.com/charmbracelet/bubbletea"
+
+	"github.com/lerko/nib/internal/db"
+	"github.com/lerko/nib/internal/display"
+)
+
+type absorbModel struct {
+	targetID string
+	sources  []*db.Entity
+	cursor   int
+	offset   int
+	height   int
+}
+
+func newAbsorbModel(targetID string) absorbModel {
+	return absorbModel{targetID: targetID}
+}
+
+func (a *absorbModel) setSources(entities []*db.Entity) {
+	a.sources = nil
+	for _, e := range entities {
+		if e.ID != a.targetID {
+			a.sources = append(a.sources, e)
+		}
+	}
+	a.cursor = 0
+	a.offset = 0
+}
+
+func (a *absorbModel) setHeight(h int) {
+	a.height = h
+}
+
+func (a absorbModel) selectedSource() *db.Entity {
+	if len(a.sources) == 0 || a.cursor >= len(a.sources) {
+		return nil
+	}
+	return a.sources[a.cursor]
+}
+
+func (a absorbModel) update(msg tea.KeyMsg) absorbModel {
+	switch msg.String() {
+	case "up", "k":
+		if a.cursor > 0 {
+			a.cursor--
+			if a.cursor < a.offset {
+				a.offset = a.cursor
+			}
+		}
+	case "down", "j":
+		if a.cursor < len(a.sources)-1 {
+			a.cursor++
+			visible := a.visibleCount()
+			if a.cursor >= a.offset+visible {
+				a.offset = a.cursor - visible + 1
+			}
+		}
+	}
+	return a
+}
+
+func (a absorbModel) view(width int) string {
+	if len(a.sources) == 0 {
+		return statusStyle.Render("no other entities")
+	}
+
+	var b strings.Builder
+	b.WriteString(titleStyle.Render("absorb into " + display.FormatID(a.targetID)))
+	b.WriteString("\n")
+	b.WriteString(helpStyle.Render("select source to merge"))
+	b.WriteString("\n\n")
+
+	visible := a.visibleCount() - 4
+	if visible <= 0 {
+		visible = 10
+	}
+	end := min(a.offset+visible, len(a.sources))
+
+	for i := a.offset; i < end; i++ {
+		e := a.sources[i]
+		line := renderAbsorbSource(e, width-4)
+
+		if i == a.cursor {
+			b.WriteString(selectedItemStyle.Render(" " + line))
+		} else {
+			b.WriteString(listItemStyle.Render(line))
+		}
+		if i < end-1 {
+			b.WriteString("\n")
+		}
+	}
+
+	return b.String()
+}
+
+func (a absorbModel) visibleCount() int {
+	if a.height <= 0 {
+		return 20
+	}
+	return a.height
+}
+
+func renderAbsorbSource(e *db.Entity, maxWidth int) string {
+	glyph := glyphStyle.Render(display.DisplayGlyph(e.Glyph, e.CardType))
+	id := idStyle.Render("[" + display.FormatID(e.ID) + "]")
+
+	body := e.Body
+	if e.Title != nil {
+		body = *e.Title
+	}
+
+	var tags string
+	if len(e.Tags) > 0 {
+		limit := min(2, len(e.Tags))
+		tagParts := make([]string, limit)
+		for i := 0; i < limit; i++ {
+			tagParts[i] = tagStyle.Render("#" + e.Tags[i])
+		}
+		tags = " " + strings.Join(tagParts, " ")
+	}
+
+	line := fmt.Sprintf("%s %s%s %s", glyph, body, tags, id)
+
+	if maxWidth > 0 && len(stripAnsi(line)) > maxWidth {
+		body = truncate(body, maxWidth-20)
+		line = fmt.Sprintf("%s %s%s %s", glyph, body, tags, id)
+	}
+
+	return line
+}