Wire bake orchestrator and CLI

Connects scan + lock + pack + write into the full pipeline. CLI entry
parses args, dispatches to bake(), prints summary or error. Five
integration tests cover fresh bake, lock-aware ID preservation,
deleted-tile tracking, oversize hard-fail, and bit-identical
determinism across re-bakes.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/bake-with-lock.test.js

@@ -0,0 +1,43 @@
+const { test } = require('node:test');
+const assert = require('node:assert');
+const path = require('node:path');
+const fs = require('node:fs');
+const os = require('node:os');
+const { bake } = require('../src/bake');
+
+const FIX = path.resolve(__dirname, 'fixtures/small-fresh');
+
+test('bake-with-lock: existing IDs preserved, new tile appended', async () => {
+    const outDir = fs.mkdtempSync(path.join(os.tmpdir(), 'atlas-bake-lock-'));
+    try {
+        // Pre-seed lock with grass=5, stone=6 (non-default IDs)
+        fs.writeFileSync(
+            path.join(outDir, 'tiles.atlas.lock.json'),
+            JSON.stringify({
+                atlas_id: 'small_demo',
+                bindings: { grass: 5, stone: 6 },
+                deleted: [],
+                next_id: 7,
+            }, null, 2),
+        );
+        const result = await bake({
+            inDir: FIX,
+            outDir,
+            atlasId: 'small_demo',
+            tileSize: 32,
+        });
+        assert.strictEqual(result.tileCount, 3);
+
+        const lock = JSON.parse(fs.readFileSync(path.join(outDir, 'tiles.atlas.lock.json'), 'utf8'));
+        assert.strictEqual(lock.bindings.grass, 5);   // preserved
+        assert.strictEqual(lock.bindings.stone, 6);   // preserved
+        assert.strictEqual(lock.bindings.water, 7);   // new
+        assert.strictEqual(lock.next_id, 8);
+
+        const atlas = JSON.parse(fs.readFileSync(path.join(outDir, 'tiles.atlas.json'), 'utf8'));
+        const ids = atlas.tiles.map(t => t.id).sort();
+        assert.deepStrictEqual(ids, [5, 6, 7]);
+    } finally {
+        fs.rmSync(outDir, { recursive: true, force: true });
+    }
+});