feat(bgm): support role= on code block info strings

Parse role.type#id from the fence info string and merge it into each
parsed object, erroring on conflicts with the content. id on the info
string can't combine with $variants. Auto-named blocks now hash their
content instead of the info string, so identical blocks dedupe.

packages/bgm/src/markdown.test.ts

@@ -39,6 +39,44 @@ describe('scanMarkdown', () => {
     expect(files[0]!.kind).toBe('yaml');
   });
 
+  it('hashes identical blocks to the same auto-name', () => {
+    const md = ['```yaml\nrole: part\n```', '', '```yaml\nrole: part\n```'].join('\n');
+    const { files } = scanMarkdown(md, 'harbor/harbor.md');
+    expect(files).toHaveLength(2);
+    expect(files[0]!.name).toBe(files[1]!.name);
+  });
+
+  it('parses role= metadata from the info string', () => {
+    const md = '```yaml file=cards.yaml role=part.poker-card\nid: 2s\n```';
+    const { files } = scanMarkdown(md, 'poker/poker.md');
+    expect(files[0]).toMatchObject({
+      name: 'poker/cards.yaml',
+      role: { role: 'part', type: 'poker-card' },
+    });
+  });
+
+  it('parses role= with type and id', () => {
+    const md = '```yaml file=board.yaml role=surface.game#main\n```';
+    const { files } = scanMarkdown(md, 'poker/poker.md');
+    expect(files[0]!.role).toEqual({ role: 'surface', type: 'game', id: 'main' });
+  });
+
+  it('parses role=package without type or id', () => {
+    const md = '```yaml file=game.yaml role=package\n```';
+    const { files } = scanMarkdown(md, 'poker/poker.md');
+    expect(files[0]!.role).toEqual({ role: 'package' });
+  });
+
+  it('throws on an unknown role=', () => {
+    const md = '```yaml file=a.yaml role=widget\n```';
+    expect(() => scanMarkdown(md, 'poker/poker.md')).toThrow(/Invalid role/);
+  });
+
+  it('throws on role=package with a type', () => {
+    const md = '```yaml file=a.yaml role=package.foo\n```';
+    expect(() => scanMarkdown(md, 'poker/poker.md')).toThrow(/Package role takes no type/);
+  });
+
   it('ignores non-definition languages', () => {
     const md = '```js\nconst x = 1;\n```';
     const { files, fences } = scanMarkdown(md, 'harbor/harbor.md');