Fix invalid \\] escape sequence in conversation.py regex

[tundakk]

Summary

The regex literal at custom_components/openclaw/conversation.py:316 is parsed by Python as two adjacent string literals rather than one. The second of those literals is non-raw and contains \], which Python 3.12+ flags as SyntaxWarning: invalid escape sequence '\]' and which Python 3.14 promotes to SyntaxError.

# Before — splits into r"\?\s*[\"'" + "»)\]]*\s*$" because the inner "" closes
# the raw string and reopens a non-raw one. The non-raw half then contains \].
if re.search(r"\?\s*[\"'""»)\]]*\s*$", text):

# After — single raw string, identical regex semantics.
if re.search(r"\?\s*[\"'»)\]]*\s*$", text):

The compiled regex character class is identical (["'»)\]]); only the Python source representation changes. The redundant inner "" was a no-op concatenation seam, not a deliberate character.

Verification

• python -W error::SyntaxWarning -c "import py_compile; py_compile.compile('conversation.py', doraise=True)" — passes after the fix, fails before.
• Regex still matches Are you sure?, Are you sure? ", Are you sure? », Are you sure?) and rejects Statement. (verified locally).
• One-line change, scoped to a cosmetic style fix; orthogonal to PR conversation: scrub OpenClaw tool_code fences before TTS #26 (behavioral scrubber change).

Test plan

• CI / maintainer's local Python ≥ 3.12 no longer emits the SyntaxWarning on import of conversation.py.
• No behavior change in _is_likely_question_followup follow-up detection.