feat(ci): add markdownlint-cli2 for consistent markdown formatting

Add automated markdown linting to ensure consistent formatting across
all markdown files in the repository.

Changes:
- Add .markdownlint-cli2.jsonc configuration
- Create .github/workflows/lint.yml for CI/CD integration
- Fix all 908 existing markdown errors across 27 files
- Enforce ATX-style headings and asterisk emphasis
- Set consistent 2-space list indentation

This prevents markdown errors after project initialization and
maintains high documentation quality standards.

templates/commands/tasks.md

@@ -106,16 +106,16 @@ Every task MUST strictly follow this format:
      - Endpoints/UI needed for that story
      - If tests requested: Tests specific to that story
    - Mark story dependencies (most stories should be independent)
-   
+
 2. **From Contracts**:
    - Map each contract/endpoint → to the user story it serves
    - If tests requested: Each contract → contract test task [P] before implementation in that story's phase
-   
+
 3. **From Data Model**:
    - Map each entity to the user story(ies) that need it
    - If entity serves multiple stories: Put in earliest story or Setup phase
    - Relationships → service layer tasks in appropriate story phase
-   
+
 4. **From Setup/Infrastructure**:
    - Shared infrastructure → Setup phase (Phase 1)
    - Foundational/blocking tasks → Foundational phase (Phase 2)
@@ -129,5 +129,3 @@ Every task MUST strictly follow this format:
   - Within each story: Tests (if requested) → Models → Services → Endpoints → Integration
   - Each phase should be a complete, independently testable increment
 - **Final Phase**: Polish & Cross-Cutting Concerns
-
-