fix: stop parsing when plugin rules do not advance

[rupayon123]

Summary

Fail fast when a block or inline rule reports a match without advancing the parser state. Previously, such a plugin could make parse() loop forever and continually allocate tokens. The guards cover block parsing, inline parsing, and inline validation (skipToken), following the behavior of markdown-it's JavaScript implementation.

Closes #441.

Validation

• Reproduced the reported block and inline hangs before the fix in child processes; both were stopped after 0.5 seconds.
• Focused progress and plugin tests: 15 passed.
• Full tests/ suite: 1,035 passed.
• Ruff 0.16.7 check and format check passed; git diff --check passed.
• The repository's benchmarking directory was not included because the reused test environment lacks its pytest-benchmark plugin; the configured tests/ suite passed.