fix(behave_shell/F.0): tighten prompt detector — log lines ending in '>' no longer vote

_detect_prompt_suffix accepted ANY line ending in $#%> as a PS1 prompt,
so a single `cat /var/log/dpkg.log` (195 lines closing in `<none>`)
flooded environmental.shell_type votes and flipped a plainly-bash
session to fish.

A prompt line now requires either a trailing space after the suffix
(default PS1 shape across bash/zsh/fish/PowerShell) or a PS1-shape
token (user@host, "PS " prefix, or a Windows drive-letter prefix).

Regression tests pin the dpkg.log false-positive and a $-terminated
prose line.

tests/profiler/behave_shell/test_prompt_line_detection.py

@@ -66,6 +66,32 @@ def test_clean_output_no_prompt() -> None:
     assert lines == []
 
 
+def test_log_lines_ending_in_gt_are_not_prompts() -> None:
+    """``dpkg.log`` style lines close with ``<none>`` — incidentally
+    ending in ``>``. They must NOT register as fish prompts; otherwise
+    a single ``cat /var/log/dpkg.log`` would flood ``shell_type`` votes
+    and flip the mode for a plainly-bash session.
+    """
+    text = (
+        "2026-05-09 02:18:09 configure libssl3:amd64 3.0.19-1~deb12u2 <none>\n"
+        "2026-05-09 02:18:09 configure libexpat1:amd64 2.5.0-1+deb12u2 <none>\n"
+        "2026-05-09 02:18:10 configure python3.11-minimal:amd64 3.11.2-6 <none>\n"
+        "root@host:~# "
+    )
+    lines = list(extract_prompt_lines(text, base_ts=10.0, max_chars=256))
+    assert len(lines) == 1
+    assert lines[0].suffix_char == "#"
+
+
+def test_output_line_ending_in_dollar_without_ps1_shape_rejected() -> None:
+    """Sentence that happens to end in ``$`` (e.g. shell variable in
+    a doc) without trailing space and without a PS1 shape token must
+    not be treated as a prompt."""
+    text = "use $PATH or $HOME\nset -- $\n"
+    lines = list(extract_prompt_lines(text, base_ts=11.0, max_chars=256))
+    assert lines == []
+
+
 def test_long_prompt_capped_to_max_chars() -> None:
     long = "x" * 500 + "$ "
     lines = list(extract_prompt_lines(long, base_ts=6.0, max_chars=256))