Fix interactive stall when a statement ends with a trailing comment

[ClaraOswald076]

Summary

Fixes #496.

In the interactive REPL, CrashBuffer.is_multiline() decides whether the
buffer stays in multiline mode by checking whether the raw input text ends
with ;. A statement with a trailing comment (select 42; -- foo) ends with
-- foo, so the condition kept the buffer in multiline mode forever and the
session stalled: pressing Enter never submitted the statement. The non
interactive path (crash -c '...') does not go through this buffer, which is
why it worked fine.

Changes

• src/crate/crash/repl.py: is_multiline now strips comments with
  sqlparse.format(text, strip_comments=True) before looking for the
  terminating semicolon. sqlparse is syntax-aware, so a ; or -- inside a
  string literal is untouched. sqlparse is already a dependency of crash,
  so no new requirements.
• tests/test_repl.py: three new CrashBufferTest cases:
  • a statement with a trailing comment is no longer multiline (regression
    test for SQL statement with trailing comment stalls in interactive session #496)
  • a statement without a semicolon is still multiline (existing behaviour)
  • a semicolon inside a string literal is still multiline (no over-matching)

Test evidence

Windows, Python 3.11.9, pytest, sqlparse 0.5.5. Pre-fix full-suite baseline:
66 passed (excluding test_integration, which needs a CrateDB server).

Before (upstream code with the new test applied):

tests/test_repl.py::CrashBufferTest::test_statement_with_trailing_comment_is_not_multiline FAILED
E       AssertionError: True is not false
========================= 1 failed, 2 passed in 0.79s =========================

After:

tests/test_repl.py::CrashBufferTest::test_statement_with_trailing_comment_is_not_multiline PASSED
============================== 4 passed in 0.41s ==============================

Full suite: 69 passed in 0.60s — no regressions.