Add infra for SGF/GIB snapshot tests

test/game_record_snapshot_tests/fixtures/README.md

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+# GameRecord Snapshot Tests
+
+This directory contains snapshot tests for `GameRecord.fromSgf` and `GameRecord.fromGib` methods.
+
+## How It Works
+
+The tests automatically discover all `.sgf` and `.gib` files in the `fixtures/` directory and validate them against their corresponding snapshot JSON files. **No need to write new test cases** - just add your file and regenerate snapshots!
+
+## Structure
+
+- `fixtures/` - Test data files
+  - `*.sgf` - Sample SGF game files
+  - `*.gib` - Sample GIB game files
+  - `snapshots/` - Expected output JSON files for comparison
+
+## Running Tests
+
+Run all snapshot tests:
+```bash
+flutter test test/game_record_snapshot_tests/
+```
+
+Or run all tests:
+```bash
+flutter test
+```
+
+## Regenerating Snapshots
+
+If you modify the `GameRecord` parsing logic or want to update the expected outputs:
+
+```bash
+dart run test/game_record_snapshot_tests/generate_snapshots.dart
+```
+
+The generator automatically discovers all `.sgf` and `.gib` files in the fixtures directory.
+
+This will regenerate all snapshot JSON files in `fixtures/snapshots/`.
+
+## Snapshot Format
+
+Each snapshot is a JSON file containing:
+```json
+{
+  "type": "GameRecordType.sgf",
+  "moveCount": 14,
+  "moves": [
+    {
+      "color": "B",  // "B" for black, "W" for white
+      "row": 4,
+      "col": 4
+    },
+    ...
+  ]
+}
+```
+
+## Adding New Test Cases
+
+1. Add a new `.sgf` or `.gib` file to `test/game_record_snapshot_tests/fixtures/`
+2. Run the generator: `dart run test/game_record_snapshot_tests/generate_snapshots.dart`
+3. Run tests to verify: `flutter test test/game_record_snapshot_tests/`
+
+**That's it!** The test framework automatically discovers and tests your new file.

test/game_record_snapshot_tests/fixtures/fox_9x9.sgf

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+(;GM[1]FF[4]
+SZ[9]
+GN[]
+DT[2025-09-16]
+PB[benjito]
+PW[V291851863]
+BR[1级]
+WR[1级]
+KM[375]HA[0]RU[Chinese]AP[GNU Go:3.8]RN[12]RE[W+4.25]TM[60]TC[3]TT[20]AP[foxwq]RL[0]
+;B[ge];W[de];B[ef];W[df];B[dg];W[ee];B[ff];W[cg];B[fc];W[dh];B[eh];W[eg];B[fg];W[dc];B[eb];W[db];B[da];W[ec];B[fb];W[ca];B[dg];W[fd];B[gd];W[eg];B[cb];W[ea];B[dg];W[ch];B[fa];W[da];B[fe];W[ed];B[eg];W[ei];B[fi];W[di])

test/game_record_snapshot_tests/fixtures/ogs_9x9.sgf

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+(;FF[4]
+CA[UTF-8]
+GM[1]
+DT[2025-11-08]
+PC[OGS: https://online-go.com/game/19728]
+GN[asdfg vs. asdf]
+PB[asdfg]
+PW[asdf]
+BR[9k]
+WR[10k]
+TM[120]OT[5x30 byo-yomi]
+RE[B+2.5]
+SZ[9]
+KM[6.5]
+RU[Japanese]
+;B[ea]
+(;W[fa]
+(;B[eb]
+(;W[fb]
+(;B[ec]
+(;W[fc]
+(;B[ed]
+(;W[fd]
+(;B[ee]
+(;W[fe]
+(;B[ef]
+(;W[ff]
+(;B[eg]
+(;W[fg]
+(;B[eh]
+(;W[fh]
+(;B[ei]
+(;W[fi]
+(;B[hh]
+(;W[hf]
+(;B[]
+(;W[]
+))))))))))))))))))))))

test/game_record_snapshot_tests/fixtures/snapshots/fox_9x9_sgf.json

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+{
+  "type": "GameRecordType.sgf",
+  "moves": [
+    {
+      "color": "B",
+      "row": 4,
+      "col": 6
+    },
+    {
+      "color": "W",
+      "row": 4,
+      "col": 3
+    },
+    {
+      "color": "B",
+      "row": 5,
+      "col": 4
+    },
+    {
+      "color": "W",
+      "row": 5,
+      "col": 3
+    },
+    {
+      "color": "B",
+      "row": 6,
+      "col": 3
+    },
+    {
+      "color": "W",
+      "row": 4,
+      "col": 4
+    },
+    {
+      "color": "B",
+      "row": 5,
+      "col": 5
+    },
+    {
+      "color": "W",
+      "row": 6,
+      "col": 2
+    },
+    {
+      "color": "B",
+      "row": 2,
+      "col": 5
+    },
+    {
+      "color": "W",
+      "row": 7,
+      "col": 3
+    },
+    {
+      "color": "B",
+      "row": 7,
+      "col": 4
+    },
+    {
+      "color": "W",
+      "row": 6,
+      "col": 4
+    },
+    {
+      "color": "B",
+      "row": 6,
+      "col": 5
+    },
+    {
+      "color": "W",
+      "row": 2,
+      "col": 3
+    },
+    {
+      "color": "B",
+      "row": 1,
+      "col": 4
+    },
+    {
+      "color": "W",
+      "row": 1,
+      "col": 3
+    },
+    {
+      "color": "B",
+      "row": 0,
+      "col": 3
+    },
+    {
+      "color": "W",
+      "row": 2,
+      "col": 4
+    },
+    {
+      "color": "B",
+      "row": 1,
+      "col": 5
+    },
+    {
+      "color": "W",
+      "row": 0,
+      "col": 2
+    },
+    {
+      "color": "B",
+      "row": 6,
+      "col": 3
+    },
+    {
+      "color": "W",
+      "row": 3,
+      "col": 5
+    },
+    {
+      "color": "B",
+      "row": 3,
+      "col": 6
+    },
+    {
+      "color": "W",
+      "row": 6,
+      "col": 4
+    },
+    {
+      "color": "B",
+      "row": 1,
+      "col": 2
+    },
+    {
+      "color": "W",
+      "row": 0,
+      "col": 4
+    },
+    {
+      "color": "B",
+      "row": 6,
+      "col": 3
+    },
+    {
+      "color": "W",
+      "row": 7,
+      "col": 2
+    },
+    {
+      "color": "B",
+      "row": 0,
+      "col": 5
+    },
+    {
+      "color": "W",
+      "row": 0,
+      "col": 3
+    },
+    {
+      "color": "B",
+      "row": 4,
+      "col": 5
+    },
+    {
+      "color": "W",
+      "row": 3,
+      "col": 4
+    },
+    {
+      "color": "B",
+      "row": 6,
+      "col": 4
+    },
+    {
+      "color": "W",
+      "row": 8,
+      "col": 4
+    },
+    {
+      "color": "B",
+      "row": 8,
+      "col": 5
+    },
+    {
+      "color": "W",
+      "row": 8,
+      "col": 3
+    }
+  ]
+}