fix(injection): send newlines as Return on the xdotool backend (#962)

* fix(injection): send newlines as Return on the xdotool backend

xdotool type maps '\n' to the Linefeed keysym, which GTK targets
silently drop — "new line" produced nothing on X11 even though the
segment reached the injector.  Split each chunk on '\n' and press
Return between typed segments so a newline lands as a real keypress
in every app.

Verified against a live GtkTextView on Xvfb: the same "A\nB" input
that previously produced 'AB' now produces 'A\nB'.

Fixes #955

* fix(commands): consume trailing punctuation after mid-utterance commands

"New paragraph." inside a longer utterance substituted correctly but
left the engine's sentence-final period typed after the break
("\\n\\n. Does this work now?").  Text-command substitution now
consumes a run of trailing , . ! ? ; : … when it precedes whitespace
or the end of the segment — the reporter's comma-phrased case
("…, new paragraph, …") stops leaking the stray comma the same way.
A mark glued to following text ("newline.io") is untouched.

Fixes #955

* fix(injection,commands): resume mid-chunk on retry, don't eat produced marks

Greptile review follow-ups on #962:

- A failed Return mid-chunk left 'typed' at the chunk start, so the
  retry re-sent text xdotool had already delivered.  'typed' now
  advances per typed segment and per Return keypress, so the retry
  resumes exactly at the un-typed position — and the clipboard
  fallback reports the same progress if retries run out.
- _TRAILING_PUNCTUATION could consume a mark produced by an earlier
  command replacement ('hello new line exclamation mark' gave '\\n'
  instead of '\\n!').  The eater now only consumes marks before
  whitespace; the end-of-utterance case ('hello new line.') is a
  pre-pass on the raw segment before any substitution runs.

* style: black-format comment indent and test condition

* fix(commands): strip segment before the end-of-utterance cleanup

Trailing whitespace ('hello new line. ') hid the final mark from the
pre-pass: the raw segment ended in a space, and the stripped segment
left the dot at end-of-string where the mid-utterance eater cannot
touch it.  Strip first, then run the cleanup.

Also add the missing type hints on the new test helper.

---------

Co-authored-by: Jatin K Malik <jatinkrmalik@gmail.com>

tests/test_command_processor.py

@@ -592,3 +592,36 @@ class TestStandaloneCommandPunctuation(unittest.TestCase):
         result, actions = self.processor.process_text("...")
         self.assertEqual(result, "...")
         self.assertEqual(actions, [])
+
+    def test_mid_utterance_trailing_punctuation_is_consumed(self) -> None:
+        """Punctuation right after a mid-utterance command does not type (#955)."""
+        cases = [
+            (
+                "Testing 1, 2, 3. New paragraph. Does this work now?",
+                "Testing 1, 2, 3. \n\n Does this work now?",
+            ),
+            (
+                "Testing 123, new paragraph, does this work now?",
+                "Testing 123, \n\n does this work now?",
+            ),
+            ("line one, new line, line two", "line one, \n line two"),
+            ("hello new line.", "hello \n"),
+            ("hello new line. ", "hello \n"),
+        ]
+        for input_text, expected in cases:
+            with self.subTest(input_text=input_text):
+                result, actions = self.processor.process_text(input_text)
+                self.assertEqual(result, expected)
+                self.assertEqual(actions, [])
+
+    def test_trailing_punct_eaten_only_before_space_or_end(self) -> None:
+        """A dot glued to following text is not sentence punctuation."""
+        result, actions = self.processor.process_text("use new paragraph.done")
+        self.assertEqual(result, "use \n\n.done")
+        self.assertEqual(actions, [])
+
+    def test_command_produced_punctuation_is_not_eaten(self) -> None:
+        """A mark from an earlier command replacement survives (#955)."""
+        result, actions = self.processor.process_text("hello new line exclamation mark")
+        self.assertEqual(result, "hello \n!")
+        self.assertEqual(actions, [])