Make --ascii escape Unicode report content

[CAOShurong]

Closes #4.

What changed

• escape every non-ASCII character in terminal reports when --ascii is set;
• preserve normal Unicode terminal and JSON output;
• add a regression test using a Unicode source path;
• release as 0.1.3 and document the fix.

Why

The public 0.1.2 wheel promises that --ascii emits no non-ASCII characters,
but a reported Unicode source path passed through unchanged on both Python 3.9
and 3.14. This made the option unsafe for genuinely ASCII-only consumers.

Verification

• public 0.1.2 baseline: the new regression test fails on Python 3.9 and 3.14
  with UnicodeEncodeError;
• candidate wheel: 20/20 fresh-environment CLI assertions pass on Python 3.9
  and 3.14, including a 251-character Unicode path, JSON preservation, normal
  terminal preservation, offline cache use, and strict ASCII decoding;
• full suite: 97 tests pass on Python 3.9 and 97 on Python 3.14;
• Ruff lint and formatting pass;
• generated README is current;
• wheel and sdist pass twine check --strict and contain version 0.1.3.

All fixtures are maintainer-controlled compatibility tests, not evidence of
external adoption.