fix: Remove duplicate method definitions in QueryCursor

[yancya]

Summary

• init_query_cursor() in ext/tree_sitter/query_cursor.c had three methods defined twice, producing Ruby warnings on require 'tree_sitter':

  warning: method redefined; discarding old exec
  warning: method redefined; discarding old match_limit
  warning: method redefined; discarding old match_limit=
  

• exec: rb_define_module_function internally defines both a singleton method and an instance method, then rb_define_method redefined the instance method → replaced with rb_define_singleton_method
• match_limit / match_limit=: DECLARE_ACCESSOR macro and explicit rb_define_method calls both defined the same methods → removed the DECLARE_ACCESSOR call

Test plan

• Added test/tree_sitter/query_cursor_test.rb that verifies no "method redefined" warnings are emitted when loading the extension
• Test fails on master (warnings present), passes with fix (warnings gone)
• bundle exec rake compile succeeds without errors

🤖 Generated with Claude Code

[stackmystack]

Thanks for the submission.
Another note on the commit message: too verbose, please remove all of the body, it's a useless read, the patch is small enough.

I can merge once patched.

[yancya]

Thanks for the review, @stackmystack!

I've addressed all the feedback:

1. Commit message: Removed the verbose body, keeping only the title.
2. Regex in test: Changed to /redefined/ as suggested.
3. DECLARE_ACCESSOR: Restored the macro and removed the explicit rb_define_method calls for match_limit/match_limit= instead.
4. Rubocop: Fixed style offenses in the test file (single quotes, %i[], &:read, argument alignment).

[yancya]

If you merge #100 first and rebase this PR, all CI tests should pass.

[stackmystack]

Thanks!