chore: Bump development version to 2.8.0-dev

After releasing v2.7.1 hotfix, development branch returns to 2.8.0-dev
for continued feature development.

Version Changes:
- pyproject.toml: 2.7.1 → 2.8.0-dev
- src/skill_seekers/__init__.py: 2.7.1 → 2.8.0-dev
- src/skill_seekers/cli/__init__.py: 2.7.1 → 2.8.0-dev
- src/skill_seekers/mcp/__init__.py: 2.7.1 → 2.8.0-dev
- src/skill_seekers/mcp/tools/__init__.py: 2.7.1 → 2.8.0-dev

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/skill_seekers/cli/__init__.py

@@ -28,7 +28,7 @@ except ImportError:
     open_folder = None
     read_reference_files = None
 
-__version__ = "2.7.1"
+__version__ = "2.8.0-dev"
 
 __all__ = [
     "LlmsTxtDetector",