refactor(runtime): author public components as template SFCs (+ integrate main)

Rewrites Box/Text/Spacer/Static/Newline from h()/render functions to Vue
<script setup> template SFCs (Transform stays a render fn — it inspects its own
child vnodes), with vue-tsc-verified consumer types (template + JSX fixtures),
provide/inject text context, the always-validate Text divergence (color +
backgroundColor), and three renderer fixes the SFCs surfaced (static anchor skip,
transform line-index Ink-parity, useBoxMetrics subtree drill). Integrates the five
main commits landed after the branch point: #163 public-API audit, generic Static
scoped-slot typing, foreground color validation, useWindowSize/divergence docs.

Squashed from the SFC sub-commits + the two main-integration merges to keep a
linear, rebaseable history. See PR #165 for the full breakdown.

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

packages/runtime/vite.config.ts

@@ -1,11 +1,39 @@
 import { defineConfig } from "vite-plus";
 import vueJsx from "@vitejs/plugin-vue-jsx";
+import Vue from "unplugin-vue/rolldown";
+import VueVite from "unplugin-vue/vite";
+
+const HOST_TAGS = ["box", "text", "virtual-text", "static", "transform"];
 
 export default defineConfig({
-  plugins: [vueJsx()],
+  // `VueVite` parses `.vue` SFCs in the TEST/dev graph (unit tests may import the
+  // .vue components directly, e.g. host/text-measure.test.ts). The `pack` build has
+  // its own `Vue` rolldown plugin below; both need `isCustomElement` so the host
+  // tags (`<box>` / `<text>` / …) inside SFC templates compile to raw element
+  // vnodes instead of being resolved as components.
+  plugins: [
+    vueJsx(),
+    VueVite({
+      template: {
+        compilerOptions: {
+          isCustomElement: (tag: string) => HOST_TAGS.includes(tag),
+        },
+      },
+    }),
+  ],
   pack: {
     entry: ["src/index.ts", "src/internal.ts"],
-    dts: true,
+    plugins: [
+      Vue({
+        isProduction: true,
+        template: {
+          compilerOptions: {
+            isCustomElement: (tag: string) => HOST_TAGS.includes(tag),
+          },
+        },
+      }),
+    ],
+    dts: { vue: true },
     exports: true,
   },
 });