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/input.go

@@ -0,0 +1,76 @@
+package tui
+
+import (
+	"github.com/charmbracelet/bubbles/textinput"
+	tea "github.com/charmbracelet/bubbletea"
+
+	"github.com/lerko/nib/internal/db"
+	"github.com/lerko/nib/internal/parse"
+)
+
+type inputModel struct {
+	ti     textinput.Model
+	active bool
+}
+
+func newInputModel() inputModel {
+	ti := textinput.New()
+	ti.Placeholder = "capture a thought…"
+	ti.Prompt = inputPromptStyle.Render("› ")
+	ti.CharLimit = 500
+	return inputModel{ti: ti}
+}
+
+func (i *inputModel) focus() {
+	i.active = true
+	i.ti.Focus()
+}
+
+func (i *inputModel) reset() {
+	i.active = false
+	i.ti.SetValue("")
+	i.ti.Blur()
+}
+
+func (i inputModel) submit() *db.Entity {
+	val := i.ti.Value()
+	if val == "" {
+		return nil
+	}
+
+	parsed, err := parse.Parse(val)
+	if err != nil {
+		return nil
+	}
+
+	e := &db.Entity{
+		Body:  parsed.Body,
+		Title: parsed.Title,
+		Glyph: db.Glyph(parsed.Glyph),
+		Tags:  parsed.Tags,
+	}
+	if parsed.TimeAnchor != nil {
+		e.TimeAnchor = parsed.TimeAnchor
+	}
+	if parsed.CardSuffix != nil {
+		ct := db.CardType(*parsed.CardSuffix)
+		e.CardType = &ct
+	}
+	if parsed.Pin {
+		e.Pinned = true
+	}
+	if parsed.Description != nil {
+		e.Description = parsed.Description
+	}
+
+	return e
+}
+
+func (i inputModel) updateKey(msg tea.KeyMsg) inputModel {
+	i.ti, _ = i.ti.Update(msg)
+	return i
+}
+
+func (i inputModel) view(width int) string {
+	return i.ti.View()
+}