feat(tui): include backlinks in link picker

Link picker now shows both outgoing [[links]] and backlinks in
a unified list with section headers. Backlinks follow by entity
ID directly, outgoing links resolve by text. Navigating into a
backlink works the same as following an outgoing link — pushes
to nav stack, esc pops back.

internal/tui/commands.go

@@ -222,6 +222,16 @@ func followLink(store *db.Store, linkText string) tea.Cmd {
 	}
 }
 
+func followLinkByID(store *db.Store, entityID string) tea.Cmd {
+	return func() tea.Msg {
+		entity, err := store.Get(context.Background(), entityID)
+		if err != nil {
+			return errMsg{err}
+		}
+		return linkFollowedMsg{entity}
+	}
+}
+
 func loadRailTags(store *db.Store) tea.Cmd {
 	return func() tea.Msg {
 		tags, err := store.ListTags(context.Background(), false)

internal/tui/linkpicker.go

@@ -3,25 +3,52 @@ package tui
 import (
 	"strings"
 
+	"github.com/lerko/nib/internal/db"
 	"github.com/lerko/nib/internal/link"
 )
 
+type linkKind int
+
+const (
+	linkOutgoing linkKind = iota
+	linkBacklink
+)
+
+type linkItem struct {
+	text     string
+	entityID string
+	kind     linkKind
+}
+
 type linkPickerModel struct {
-	links  []string
+	items  []linkItem
 	cursor int
 }
 
-func newLinkPicker(body string) linkPickerModel {
-	return linkPickerModel{
-		links: link.ExtractLinks(body),
+func newLinkPicker(body string, backlinks []db.Backlink) linkPickerModel {
+	var items []linkItem
+
+	for _, lt := range link.ExtractLinks(body) {
+		items = append(items, linkItem{text: lt, kind: linkOutgoing})
 	}
+	for _, bl := range backlinks {
+		label := bl.Body
+		if bl.Title != nil {
+			label = *bl.Title
+		} else if len(label) > 50 {
+			label = label[:50] + "…"
+		}
+		items = append(items, linkItem{text: label, entityID: bl.EntityID, kind: linkBacklink})
 	}
 
-func (lp linkPickerModel) selected() string {
-	if len(lp.links) == 0 || lp.cursor >= len(lp.links) {
-		return ""
+	return linkPickerModel{items: items}
 }
-	return lp.links[lp.cursor]
+
+func (lp linkPickerModel) selected() linkItem {
+	if len(lp.items) == 0 || lp.cursor >= len(lp.items) {
+		return linkItem{}
+	}
+	return lp.items[lp.cursor]
 }
 
 func (lp linkPickerModel) update(key string) linkPickerModel {
@@ -31,7 +58,7 @@ func (lp linkPickerModel) update(key string) linkPickerModel {
 			lp.cursor--
 		}
 	case "down", "j":
-		if lp.cursor < len(lp.links)-1 {
+		if lp.cursor < len(lp.items)-1 {
 			lp.cursor++
 		}
 	}
@@ -42,15 +69,31 @@ func (lp linkPickerModel) view(width int) string {
 	var b strings.Builder
 	b.WriteString(titleStyle.Render("follow link") + "\n\n")
 
-	if len(lp.links) == 0 {
-		b.WriteString(hintDescStyle.Render("  no [[links]] in this entry"))
+	if len(lp.items) == 0 {
+		b.WriteString(hintDescStyle.Render("  no links or backlinks"))
 		b.WriteString("\n\n")
 		b.WriteString(helpStyle.Render("esc:back"))
 		return b.String()
 	}
 
-	for i, lt := range lp.links {
-		label := "[[" + lt + "]]"
+	prevKind := linkKind(-1)
+	for i, item := range lp.items {
+		if item.kind != prevKind {
+			if item.kind == linkOutgoing {
+				b.WriteString(dateHeaderStyle.Render("── outgoing ──") + "\n")
+			} else {
+				b.WriteString(dateHeaderStyle.Render("── backlinks ──") + "\n")
+			}
+			prevKind = item.kind
+		}
+
+		var label string
+		if item.kind == linkOutgoing {
+			label = "[[" + item.text + "]]"
+		} else {
+			label = "← " + item.text
+		}
+
 		if i == lp.cursor {
 			b.WriteString(selectedItemStyle.Render(" " + label))
 		} else {

internal/tui/model.go

@@ -860,7 +860,7 @@ func (m model) updateBrowse(msg tea.KeyMsg) (tea.Model, tea.Cmd) {
 
 	case "[":
 		if m.state == stateDetail && m.detail.entity != nil && m.detail.mode == detailPreview {
-			m.linkPicker = newLinkPicker(m.detail.entity.Body)
+			m.linkPicker = newLinkPicker(m.detail.entity.Body, m.detail.backlinks)
 			m.state = stateLinkPicker
 			return m, nil
 		}
@@ -964,14 +964,17 @@ func (m model) updateLinkPicker(msg tea.KeyMsg) (tea.Model, tea.Cmd) {
 		m.state = stateDetail
 		return m, nil
 	case "enter":
-		lt := m.linkPicker.selected()
-		if lt == "" {
+		item := m.linkPicker.selected()
+		if item.text == "" && item.entityID == "" {
 			return m, nil
 		}
 		if m.detail.entity != nil {
 			m.navStack = append(m.navStack, m.detail.entity.ID)
 		}
-		return m, followLink(m.store, lt)
+		if item.kind == linkBacklink {
+			return m, followLinkByID(m.store, item.entityID)
+		}
+		return m, followLink(m.store, item.text)
 	default:
 		m.linkPicker = m.linkPicker.update(msg.String())
 		return m, nil