chore: Bump version to 2.8.0-dev

Start development cycle for v2.8.0.

Version updated in 5 locations:
- pyproject.toml
- src/skill_seekers/__init__.py
- src/skill_seekers/cli/__init__.py
- src/skill_seekers/mcp/__init__.py
- src/skill_seekers/mcp/tools/__init__.py

All version numbers synchronized to prevent Issue #248.

[Unreleased] section in CHANGELOG.md ready for v2.8.0 changes.

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__ = "2.7.0"
+__version__ = "2.8.0-dev"
 
 __all__ = [
     "LlmsTxtDetector",