fix: convert periods to hyphens in kebab_filenames mode

Fixes #423

- Replace periods with hyphens before calling generate_permalink() to prevent os.path.splitext() confusion
- Convert Entity.file_path from @Property to @computed_field so it's included in model_dump()
- Add comprehensive test suite with 19 tests covering all kebab-case transformations

🤖 Generated with Claude Code (https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: divideby0

src/basic_memory/schemas/base.py

@@ -21,7 +21,7 @@
 from annotated_types import MinLen, MaxLen
 from dateparser import parse
 
-from pydantic import BaseModel, BeforeValidator, Field, model_validator
+from pydantic import BaseModel, BeforeValidator, Field, model_validator, computed_field
 
 from basic_memory.config import ConfigManager
 from basic_memory.file_utils import sanitize_for_filename, sanitize_for_folder
@@ -232,12 +232,16 @@ def safe_title(self) -> str:
         use_kebab_case = app_config.kebab_filenames
 
         if use_kebab_case:
-            fixed_title = generate_permalink(file_path=fixed_title, split_extension=False)
+            # Replace periods with hyphens first to prevent os.path.splitext from treating them as extensions
+            # This is necessary because generate_permalink was designed for file paths, not bare titles
+            fixed_title = fixed_title.replace('.', '-')
+            fixed_title = generate_permalink(file_path=fixed_title, split_extension=True)
 
         return fixed_title
 
+    @computed_field
     @property
-    def file_path(self):
+    def file_path(self) -> str:
         """Get the file path for this entity based on its permalink."""
         safe_title = self.safe_title
         if self.content_type == "text/markdown":