fix: Framework detection now works by including import-only files (fixes #239)

## Problem
Framework detection was broken because files with only imports (no
classes/functions) were excluded from analysis. The architectural pattern
detector received empty file lists, resulting in 0 frameworks detected.

## Root Cause
In codebase_scraper.py:873-881, the has_content check filtered out files
that didn't have classes, functions, or other structural elements. This
excluded simple __init__.py files that only contained import statements,
which are critical for framework detection.

## Solution (3 parts)

1. **Extract imports from Python files** (code_analyzer.py:140-178)
   - Added import extraction using AST (ast.Import, ast.ImportFrom)
   - Returns imports list in analysis results
   - Now captures: "from flask import Flask" → ["flask"]

2. **Include import-only files** (codebase_scraper.py:873-881)
   - Updated has_content check to include files with imports
   - Files with imports are now included in analysis results
   - Comment added: "IMPORTANT: Include files with imports for framework
     detection (fixes #239)"

3. **Enhance framework detection** (architectural_pattern_detector.py:195-240)
   - Extract imports from all Python files in analysis
   - Check imports in addition to file paths and directory structure
   - Prioritize import-based detection (high confidence)
   - Require 2+ matches for path-based detection (avoid false positives)
   - Added debug logging: "Collected N imports for framework detection"

## Results

**Before fix:**
- Test Flask project: 0 files analyzed, 0 frameworks detected
- Files with imports: excluded from analysis
- Framework detection: completely broken

**After fix:**
- Test Flask project: 3 files analyzed, Flask detected ✅
- Files with imports: included in analysis
- Framework detection: working correctly
- No false positives (ASP.NET, Rails, etc.)

## Testing

Added comprehensive test suite (tests/test_framework_detection.py):
- ✅ test_flask_framework_detection_from_imports
- ✅ test_files_with_imports_are_included
- ✅ test_no_false_positive_frameworks

All existing tests pass:
- ✅ 38 tests in test_codebase_scraper.py
- ✅ 54 tests in test_code_analyzer.py
- ✅ 3 new tests in test_framework_detection.py

## Impact

- Fixes issue #239 completely
- Framework detection now works for Python projects
- Import-only files (common in Python packages) are properly analyzed
- No performance impact (import extraction is fast)
- No breaking changes to existing functionality

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

src/skill_seekers/cli/code_analyzer.py

@@ -147,6 +147,7 @@ class CodeAnalyzer:
 
         classes = []
         functions = []
+        imports = []
 
         for node in ast.walk(tree):
             if isinstance(node, ast.ClassDef):
@@ -171,11 +172,24 @@ class CodeAnalyzer:
                 if not is_method:
                     func_sig = self._extract_python_function(node)
                     functions.append(asdict(func_sig))
+            elif isinstance(node, ast.Import):
+                # Extract: import foo, bar
+                for alias in node.names:
+                    imports.append(alias.name)
+            elif isinstance(node, ast.ImportFrom):
+                # Extract: from foo import bar
+                module = node.module or ""
+                imports.append(module)
 
         # Extract comments
         comments = self._extract_python_comments(content)
 
-        return {"classes": classes, "functions": functions, "comments": comments}
+        return {
+            "classes": classes,
+            "functions": functions,
+            "comments": comments,
+            "imports": imports,  # Include imports for framework detection
+        }
 
     def _extract_python_class(self, node: ast.ClassDef) -> ClassSignature:
         """Extract class signature from AST node."""