1. Types

• [x] 1.1 Add collapsed?: boolean to SidebarItem interface in src/types.ts
• [x] 1.2 Add NavItem type ({ text: string, link: string }) to src/types.ts
• [x] 1.3 Update OpenSpecPluginOptions to accept optional text field for nav label override

2. Tag-Grouped Sidebar

• [x] 2.1 In src/utils.ts, create groupEndpointsByTag(endpoints: ParsedEndpoint[]) that groups endpoints by their first tag (fallback: "Other") and sorts groups alphabetically
• [x] 2.2 Update generateSidebarFromSpec() to call groupEndpointsByTag() and return { text, collapsed: false, items }[] instead of a flat array
• [x] 2.3 Write/update tests in src/__tests__/utils.test.ts to assert grouped sidebar output shape

3. Index Page Summary Table

• [x] 3.1 Update generateIndexMarkdown() in src/utils.ts to append a | Method | Path | Summary | table after the existing heading and links
• [x] 3.2 Sort table rows by tag (alphabetical) then path (alphabetical)
• [x] 3.3 Write/update tests to assert the table is present in index page output

4. openspecNav Helper

• [x] 4.1 Add openspecNav(options: { spec: string, outDir: string, text?: string }): NavItem function to src/utils.ts
• [x] 4.2 Implement: load spec via existing loadSpec(), read info.title as default text, derive link as /${outDir}/
• [x] 4.3 Throw descriptive error when spec file is not found (include path in message)
• [x] 4.4 Export openspecNav from src/index.ts
• [x] 4.5 Write tests for openspecNav covering default label, custom label, and missing-file error

5. Build & Validation

• [x] 5.1 Run npm run lint and fix any TypeScript errors
• [x] 5.2 Run npm test and confirm all tests pass
• [x] 5.3 Run npm run build and confirm ESM + CJS output includes openspecNav export