Add saved starter words for signed-in players

Players can save up to 3 favorite opening words and tap one to fill the
current row. Words are stored on profiles.starter_words and saved through
the set_starter_words RPC, which validates them against the dictionary.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/fancy-wordle.spec.js

@@ -116,3 +116,48 @@ test("definition lookup leaves loading state when a provider times out", async (
     timeout: 6500
   })
 })
+
+test("guests are prompted to sign in to save starter words", async ({ page }) => {
+  await openApp(page)
+  await skipIntro(page)
+
+  const starterPanel = page.locator("#starter-panel")
+  await expect(starterPanel).toBeVisible()
+  await expect(starterPanel).toContainText("to save up to 3 favorite openers")
+  await expect(page.locator("#starter-edit")).toBeHidden()
+
+  await starterPanel.locator("[data-starter-sign-in]").click()
+  await expect(page.locator("#auth-modal")).toBeVisible()
+})
+
+test("starter words fill the current row and the editor keeps keys off the board", async ({ page }) => {
+  await page.route("**/rest/v1/rpc/set_starter_words", route => route.fulfill({ json: ["crane", "arise"] }))
+  await openApp(page)
+  await skipIntro(page)
+  await expect(page.locator("#round-status")).not.toContainText("Loading")
+
+  await page.evaluate(() => {
+    authSession = { user: { id: "test-user", email: "player@example.test" } }
+    starterWords = ["plane", "arise"]
+    starterWordsLoaded = true
+    renderStarterPanel()
+  })
+
+  const readFirstRow = () => page.locator("[data-guess-grid] .tile").evaluateAll(tiles =>
+    tiles.slice(0, 5).map(tile => tile.dataset.letter || "").join("")
+  )
+
+  await page.keyboard.press("Q")
+  await page.locator("[data-starter-word='arise']").click()
+  expect(await readFirstRow()).toBe("arise")
+
+  await page.locator("#starter-edit").click()
+  const firstInput = page.locator(".starter-input").first()
+  await expect(firstInput).toHaveValue("plane")
+  await firstInput.fill("crane")
+  await firstInput.press("Enter")
+
+  await expect(page.locator("[data-alert-container]")).toContainText("Starter words saved")
+  await expect(page.locator("[data-starter-word]")).toHaveText(["crane", "arise"])
+  expect(await readFirstRow()).toBe("arise")
+})