feat: improve opening trainer flow and add deviation dialog

- Add tutor message guardrail to prevent rapid-fire messages
  - Track last message by move index
  - Wait for both player and opponent moves before speaking
  - Speak immediately when player deviates from theory

- Add deviation dialog with three options:
  - Continue Playing (Start Game) - transitions to game mode
  - Undo & Return to Opening - returns to theory
  - Explore This Variation - continues off-book practice

- Implement smooth game mode transition:
  - Pass opening context from trainer to game
  - Tutor welcomes player with context about their study
  - Computer makes first move if needed in starting position

- Fix generate-test-fixtures script:
  - Add safety check to prevent overwriting real data
  - Restore full opening database (12,379 openings)
  - Rebuild move index (12,377 sequences)
  - Add clear warnings about test fixtures

- Update ChessGame to accept openingContext prop
- Update Tutor to display contextual greeting in game mode

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

e2e/fixtures/openings/ecoA.json

@@ -0,0 +1,48 @@
+{
+  "rn1qkbnr/ppp2ppp/8/3p4/5p2/6PB/PPPPP2P/RNBQK2R w KQkq - 0 5": {
+    "src": "eco_tsv",
+    "eco": "A00",
+    "moves": "1. Nh3 d5 2. g3 e5 3. f4 Bxh3 4. Bxh3 exf4",
+    "name": "Amar Gambit"
+  },
+  "rnbqkbnr/pppppppp/8/8/8/7N/PPPPPPPP/RNBQKB1R b KQkq - 1 1": {
+    "src": "eco_tsv",
+    "eco": "A00",
+    "moves": "1. Nh3",
+    "name": "Amar Opening",
+    "scid": "A00g",
+    "aliases": {
+      "scid": "Amar/Paris Opening",
+      "eco_wikip": "Irregular Openings: Amar Opening",
+      "ct": "Amar Opening, General",
+      "chessGraph": "Amar; Paris Opening",
+      "chronos": "Amar (Paris) opening",
+      "icsbot": "Amar; Paris Opening "
+    }
+  },
+  "rn1qkbnr/ppp2ppp/8/3p4/8/6PB/PPPPP3/RNBQ1RK1 b kq - 0 6": {
+    "src": "eco_tsv",
+    "eco": "A00",
+    "moves": "1. Nh3 d5 2. g3 e5 3. f4 Bxh3 4. Bxh3 exf4 5. O-O fxg3 6. hxg3",
+    "name": "Amar Opening: Paris Gambit, Gent Gambit",
+    "aliases": {
+      "ct": "Amar Opening, Gent Gambit"
+    }
+  },
+  "rnbqkbnr/ppp2ppp/8/3pp3/5P2/6PN/PPPPP2P/RNBQKB1R b KQkq - 0 3": {
+    "src": "eco_tsv",
+    "eco": "A00",
+    "moves": "1. Nh3 d5 2. g3 e5 3. f4",
+    "name": "Amar Opening: Paris Gambit",
+    "scid": "A00g",
+    "aliases": {
+      "scid": "Amar: Paris Gambit"
+    }
+  },
+  "r1bqkb1r/ppp2ppp/2np1n2/4p3/2P5/1PN1P3/P2P1PPP/R1BQKBNR w KQkq - 1 5": {
+    "src": "eco_tsv",
+    "eco": "A00",
+    "moves": "1. e3 e5 2. c4 d6 3. Nc3 Nc6 4. b3 Nf6",
+    "name": "Amsterdam Attack"
+  }
+}