Anglicize tippen's codebase and finish pending UI/curriculum cleanup

- Rename all German identifiers, types, mode ids, file names, CSS classes
  and data-attributes to English throughout tippen/src; only user-facing
  text (lesson titles, word lists, labels, spoken praise) stays German.
- Add a word/nonsense-word list to the "Übung: die Grundstellung" home-row
  lesson in the curriculum.
- Remove the unused HandHint component and speech.ts, and carry forward
  the in-progress App.tsx/component/generator/progress edits from other
  sessions.
- Refresh the regenerated music-library cache index.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

tippen/src/lib/__tests__/fingers.test.ts

@@ -2,7 +2,7 @@ import { describe, expect, it } from "vitest";
 
 import {
   FINGERS,
-  GRUNDSTELLUNG,
+  HOME_ROW,
   KEYBOARD_ROWS,
   fingerOf,
   handOf,
@@ -23,9 +23,9 @@ describe("fingerOf", () => {
     for (const key of ALPHABET) {
       // "ß".toUpperCase() is "SS" - two characters, and not a key. `event.key` never
       // reports that, so the single-character case is the one that has to hold.
-      const gross = key.toUpperCase();
-      if ([...gross].length !== 1) continue;
-      expect(fingerOf(gross)?.id, gross).toBe(fingerOf(key)?.id);
+      const upper = key.toUpperCase();
+      if ([...upper].length !== 1) continue;
+      expect(fingerOf(upper)?.id, upper).toBe(fingerOf(key)?.id);
     }
   });
 
@@ -33,44 +33,44 @@ describe("fingerOf", () => {
     for (const key of ["Enter", "F1", "€", ""]) expect(fingerOf(key)).toBeNull();
   });
 
-  it("assigns the Grundstellung to the eight home fingers, left to right", () => {
+  it("assigns the home row to the eight home fingers, left to right", () => {
     const expected = [
-      "links-klein",
-      "links-ring",
-      "links-mitte",
-      "links-zeige",
-      "rechts-zeige",
-      "rechts-mitte",
-      "rechts-ring",
-      "rechts-klein",
+      "left-pinky",
+      "left-ring",
+      "left-middle",
+      "left-index",
+      "right-index",
+      "right-middle",
+      "right-ring",
+      "right-pinky",
     ];
-    GRUNDSTELLUNG.forEach((key, i) => expect(fingerOf(key)?.id).toBe(expected[i]));
+    HOME_ROW.forEach((key, i) => expect(fingerOf(key)?.id).toBe(expected[i]));
   });
 
   it("gives each finger the home key it actually rests on", () => {
-    for (const key of GRUNDSTELLUNG) expect(homeKeyOf(key)).toBe(key);
+    for (const key of HOME_ROW) expect(homeKeyOf(key)).toBe(key);
     expect(homeKeyOf(" ")).toBe(" ");
   });
 
   it("sends the two index fingers to their stretch keys", () => {
-    for (const key of "rtfgvb") expect(fingerOf(key)?.id).toBe("links-zeige");
-    for (const key of "zuhjnm") expect(fingerOf(key)?.id).toBe("rechts-zeige");
+    for (const key of "rtfgvb") expect(fingerOf(key)?.id).toBe("left-index");
+    for (const key of "zuhjnm") expect(fingerOf(key)?.id).toBe("right-index");
   });
 });
 
 describe("hands", () => {
   it("splits the letters into two disjoint, non-empty sets", () => {
-    const links = [...ALPHABET].filter((key) => handOf(key) === "links");
-    const rechts = [...ALPHABET].filter((key) => handOf(key) === "rechts");
-    expect(links.length).toBeGreaterThan(0);
-    expect(rechts.length).toBeGreaterThan(0);
-    expect(links.length + rechts.length).toBe(ALPHABET.length);
-    expect(links.some((key) => rechts.includes(key))).toBe(false);
+    const left = [...ALPHABET].filter((key) => handOf(key) === "left");
+    const right = [...ALPHABET].filter((key) => handOf(key) === "right");
+    expect(left.length).toBeGreaterThan(0);
+    expect(right.length).toBeGreaterThan(0);
+    expect(left.length + right.length).toBe(ALPHABET.length);
+    expect(left.some((key) => right.includes(key))).toBe(false);
   });
 
   it("shifts with the opposite hand", () => {
-    expect(shiftHandFor("a")).toBe("rechts");
-    expect(shiftHandFor("l")).toBe("links");
+    expect(shiftHandFor("a")).toBe("right");
+    expect(shiftHandFor("l")).toBe("left");
     expect(shiftHandFor("Enter")).toBeNull();
   });
 });
@@ -80,8 +80,8 @@ describe("rows", () => {
     for (const key of ALPHABET) expect(rowOf(key), key).not.toBeNull();
   });
 
-  it("has the Grundstellung in the Grundreihe", () => {
-    for (const key of GRUNDSTELLUNG) expect(rowOf(key)).toBe("grund");
+  it("has the home row in the home row", () => {
+    for (const key of HOME_ROW) expect(rowOf(key)).toBe("home");
   });
 
   it("draws three rows, each with keys", () => {