feat: auto-capitalize sentences after punctuation (#554)

* feat: auto-capitalize sentences after punctuation

Add capitalize_sentences() function that uppercases the first letter of
dictated text and after sentence-ending punctuation (., !, ?) followed by
whitespace. Preserves URLs, decimals, and abbreviations without trailing space.

- Config option text_injection.auto_capitalize (default: true)
- Settings toggle in General tab to opt out
- 17 tests covering edge cases

Fixes #553

* style: black-format auto-capitalize helpers for CI lint

Fixes the Lint Python check failure on the auto-capitalize PR.

* refactor: make auto-capitalize Vosk-only with clear UI indication

- Gate auto-capitalize feature to Vosk engine only (Whisper outputs proper casing)
- Update settings tooltip to explain Vosk-only behavior
- Update subtitle to show '(Vosk only)' for user clarity

* test(main): cover Vosk-only auto-capitalize injection path

Add callback wiring tests for enabled/disabled auto-capitalize on Vosk
and the Whisper skip path so codecov patch coverage clears the 80% bar.

Co-authored-by: Jatin K Malik <jatinkrmalik@users.noreply.github.com>

* refactor(settings): move Auto-Capitalize to Recognition tab

Auto-capitalize is dictation output post-processing, not application
lifecycle behavior, so it belongs alongside Voice Commands rather than
with autostart/clipboard settings in General.

Co-authored-by: Jatin K Malik <jatinkrmalik@users.noreply.github.com>

---------

Co-authored-by: Cursor Agent <cursoragent@cursor.com>
Co-authored-by: Jatin K Malik <jatinkrmalik@users.noreply.github.com>

src/vocalinux/speech_recognition/command_processor.py

@@ -304,3 +304,31 @@ class CommandProcessor:
                         processed_text = ""
 
         return processed_text, actions
+
+
+def capitalize_sentences(text: str) -> str:
+    """Capitalize the first letter of each sentence.
+
+    Uppercases the first character of the string and any lowercase letter
+    that follows sentence-ending punctuation (``.``, ``!``, ``?``) plus
+    whitespace.  Leaves URLs, decimals, and abbreviations without trailing
+    space untouched.
+
+    Args:
+        text: The text to capitalize.
+
+    Returns:
+        The text with sentence-initial letters uppercased.
+    """
+    if not text:
+        return text
+
+    # Capitalize first character
+    result = text[0].upper() + text[1:]
+
+    # Capitalize after sentence-ending punctuation + whitespace
+    result = re.sub(
+        r"([.!?])(\s+)([a-z])", lambda m: m.group(1) + m.group(2) + m.group(3).upper(), result
+    )
+
+    return result