Document how to disable screen reader functionality using speak_text variable

docs/components/AssemblyLine/magic_variables.md

@@ -448,6 +448,48 @@ argument and calls Docassemble's `set_language()` function.
 This event is used internally by the language switching functions like
 `get_language_list_dropdown()` and `get_language_list()`.
 
+### Screen reader control
+
+#### `speak_text`
+
+Controls whether the Assembly Line's built-in screen reader functionality is enabled.
+The screen reader feature was added not primarily for blind users, but for people with
+low literacy and users on shared workstations or when borrowing mobile devices.
+
+Defaults to `True` (screen reader enabled). Set to `False` to disable the text-to-speech
+functionality for the interview.
+
+```yaml
+code: |
+  speak_text = False
+```
+
+This can be set on a per-interview basis in any mandatory code block or in the
+interview order block. For organization-wide control, you can set this variable
+in a shared YAML file that all your interviews include.
+
+**Per-interview example:**
+```yaml
+---
+mandatory: True
+code: |
+  speak_text = False
+  # ... rest of your interview order
+---
+```
+
+**Organization-wide example (in a shared file):**
+```yaml
+---
+code: |
+  speak_text = False
+---
+```
+
+Note: This setting controls the Assembly Line's screen reader feature. For more information
+about Docassemble's built-in text-to-speech functionality, see the
+[Docassemble documentation](https://docassemble.org/docs/special.html#speak_text).
+
 ## Run-time options
 
 These options are ones that you can sometimes configure when you author the