docs: fix an inverted comment in the quiz-form example

The comment in final_form/app.py said ReactPy 'still submits the form's
defaults' when preventDefault() is detected -- the opposite of what it does. It
suppresses the default navigation, which is the only reason the async handler
survives long enough to render the result. Verified in Chrome: submitting stays
on the page (pathname '/'), the textarea and button lock during the await, and
the error paragraph appears after it resolves.

Measured prevent_default detection on the shipped bytecode: direct call True,
async handler awaiting after the call True, call hidden in a helper False,
rebound argument False -- so the comment's warning about indirection is now
stated explicitly.

Also correct running-tests.md's summary bullet that called the docs checks a
gate on every pull request; nothing gates them (see about/code.md).

Author: Archmonger

docs/examples/reacting_to_input_with_state/final_form/app.py

@@ -22,9 +22,11 @@ def form():
         return html.h1("That's right!")
 
     async def handle_submit(event):
-        # Awaiting inside the handler is fine: ReactPy still submits the form's
-        # defaults because it detects preventDefault() from the handler's code,
-        # not from when it runs.
+        # Awaiting inside the handler is fine: ReactPy still suppresses the
+        # form's default navigation, because it detects the preventDefault()
+        # call by reading this function's bytecode -- whether or not the handler
+        # ever finishes does not matter. The call must appear in this function
+        # itself, though: hiding it in a helper defeats the inspection.
         event.preventDefault()
         set_status("submitting")
         try:

docs/src/about/running-tests.md

@@ -9,7 +9,7 @@ There are two test suites in this project, and they live in different places. Th
 !!! summary "You will learn"
 
     -   How to run the Python test suite, and why it needs a browser installed
-    -   How to run the documentation build checks that gate every docs pull request
+    -   How to run the documentation build checks yourself, since no CI runs them for you
     -   Which command failures are yours and which are environmental
 
 !!! abstract "Note"