feat(tui): add bubbletea terminal UI with entity list, detail, and capture

Adds `nib tui` command and `make tui` target. Scrollable entity list
with j/k navigation, enter for detail view, `a` to capture new entries
using the existing parse grammar, and `d` to delete.

internal/tui/detail.go

@@ -0,0 +1,106 @@
+package tui
+
+import (
+	"fmt"
+	"strings"
+	"time"
+
+	tea "github.com/charmbracelet/bubbletea"
+
+	"github.com/lerko/nib/internal/db"
+	"github.com/lerko/nib/internal/display"
+)
+
+type detailModel struct {
+	entity *db.Entity
+	scroll int
+	height int
+	width  int
+}
+
+func newDetailModel() detailModel {
+	return detailModel{}
+}
+
+func (d *detailModel) setEntity(e *db.Entity) {
+	d.entity = e
+	d.scroll = 0
+}
+
+func (d *detailModel) setSize(width, height int) {
+	d.width = width
+	d.height = height
+}
+
+func (d detailModel) update(msg tea.KeyMsg) detailModel {
+	switch msg.String() {
+	case "up", "k":
+		if d.scroll > 0 {
+			d.scroll--
+		}
+	case "down", "j":
+		d.scroll++
+	}
+	return d
+}
+
+func (d detailModel) view(width int) string {
+	if d.entity == nil {
+		return ""
+	}
+
+	e := d.entity
+	var b strings.Builder
+
+	glyph := display.DisplayGlyph(e.Glyph, e.CardType)
+	header := fmt.Sprintf("%s  %s", glyph, display.FormatID(e.ID))
+	b.WriteString(detailHeaderStyle.Render(header))
+	b.WriteString("\n\n")
+
+	if e.Title != nil {
+		b.WriteString(detailBodyStyle.Render("title: " + *e.Title))
+		b.WriteString("\n")
+	}
+
+	b.WriteString(detailBodyStyle.Render(e.Body))
+	b.WriteString("\n")
+
+	if len(e.Tags) > 0 {
+		tagParts := make([]string, len(e.Tags))
+		for i, t := range e.Tags {
+			tagParts[i] = tagStyle.Render("#" + t)
+		}
+		b.WriteString("\n")
+		b.WriteString(detailBodyStyle.Render(strings.Join(tagParts, " ")))
+		b.WriteString("\n")
+	}
+
+	b.WriteString("\n")
+	meta := fmt.Sprintf("created  %s", e.CreatedAt.Format(time.DateTime))
+	if e.ModifiedAt != e.CreatedAt {
+		meta += fmt.Sprintf("\nmodified %s", e.ModifiedAt.Format(time.DateTime))
+	}
+	if e.TimeAnchor != nil {
+		meta += fmt.Sprintf("\nanchored @%s", *e.TimeAnchor)
+	}
+	if e.Pinned {
+		meta += "\npinned"
+	}
+	if e.CardType != nil {
+		meta += fmt.Sprintf("\ncard     %s", *e.CardType)
+	}
+	if e.CompletedAt != nil {
+		meta += fmt.Sprintf("\ndone     %s", e.CompletedAt.Format(time.DateTime))
+	}
+	b.WriteString(idStyle.Render(meta))
+
+	lines := strings.Split(b.String(), "\n")
+	if d.scroll > 0 && d.scroll < len(lines) {
+		lines = lines[d.scroll:]
+	}
+	if d.height > 0 && len(lines) > d.height {
+		lines = lines[:d.height]
+	}
+
+	return strings.Join(lines, "\n")
+}