feat(web): charmbracelet-aesthetic tapir spinner with charm palette

Replace the plain ASCII spinner with a Charmbracelet-style TUI panel rendered in
the browser: a dark terminal card holding a rounded purple box (╭─╮╰─╯│) around a
pink block-char tapir (▄▓▀█) with mint eyes (◕ ◕) and a snout that wiggles ∩→∪→~
across three cross-faded frames, plus a lipgloss-style progress bar whose mint
fill grows over a dim track via an 8s CSS clip animation.

Colours come from named palette consts (CharmPurple/Pink/Mint/Cream/Dim) applied
as inline span styles, so the box and CSS share one source of truth. Frames are
built by a small run/line helper that pads each row to a fixed interior width —
an internal test asserts every box row is the same cell width so the border stays
flush. Honours prefers-reduced-motion (static frame + partial bar).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

internal/web/view_internal_test.go

@@ -1,6 +1,11 @@
 package web
 
-import "testing"
+import (
+	"regexp"
+	"strings"
+	"testing"
+	"unicode/utf8"
+)
 
 func TestEmbedURL(t *testing.T) {
 	tests := []struct {
@@ -27,3 +32,19 @@ func TestEmbedURL(t *testing.T) {
 		})
 	}
 }
+
+// TestTapirFrameRowsAligned asserts every box row has the same cell width once
+// the inline-colour spans are stripped, so the rounded border lines up on every
+// line (the panel only looks right if the right │ is flush across all rows).
+func TestTapirFrameRowsAligned(t *testing.T) {
+	stripSpan := regexp.MustCompile(`</?span[^>]*>`)
+	for name, frame := range map[string]string{"f1": tapirFrameHTML1, "f2": tapirFrameHTML2, "f3": tapirFrameHTML3} {
+		plain := stripSpan.ReplaceAllString(frame, "")
+		want := tapirInteriorW + 2 // both purple side borders
+		for i, line := range strings.Split(plain, "\n") {
+			if got := utf8.RuneCountInString(line); got != want {
+				t.Errorf("%s line %d width = %d, want %d: %q", name, i, got, want, line)
+			}
+		}
+	}
+}