Rewrite Python comments in Google developer documentation style (#12)

* Rewrite comments in Google developer documentation style

Rewrite the comments and docstrings across the backend core modules so they
read plainly. The previous prose was accurate but dense and figurative, which
made it slow to skim.

Applies the Google developer documentation style guide: short sentences, active
voice, present tense, American spelling, and no metaphors, idioms, or
rhetorical asides. Replaces em-dash chains with separate sentences.

backend/app/routers/scripts.py

@@ -84,7 +84,7 @@ def test_script(
     db: Session = Depends(get_db),
     user: models.User = Depends(auth.get_current_user),
 ):
-    """Dry-run one hook against sample text — no AI call, no persistence."""
+    """Runs one hook against sample text, making no AI call and storing nothing."""
     script = get_script_or_404(script_id, db, user)
     limits.rate_limit("script-test", request, user)
     result = run_hook(
@@ -145,7 +145,8 @@ def import_script(
 
     script = models.Script(
         user_id=user.id,
-        # Raw-dict import bypasses the schemas — clamp to the VARCHAR width.
+        # A raw-dict import bypasses the schemas, so truncate to the VARCHAR
+        # width.
         name=(pick("name") or "Imported Script")[:schemas.NAME_MAX],
         description=pick("description"),
         library_js=pick("library", "library_js", "sharedLibrary"),