Fix reaction parsing for +1/-1 values in YAML (#4891)

* Initial plan

* Initial plan for fixing reaction parsing bug

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

* Fix reaction parsing for +1/-1 values in YAML

- Update JSON schema to accept both string and integer types for reaction field
- Handle int64 and uint64 types when parsing reaction values from frontmatter
- Quote reaction value in generated lock.yml to prevent YAML re-parsing issues
- Add tests for numeric reaction parsing (+1/-1 without quotes)
- Update existing tests to expect quoted reaction values

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

* Refactor reaction parsing: extract helper functions and improve test comments

- Extract parseReactionValue and intToReactionString helper functions
- Add comprehensive unit tests for the new helper functions
- Fix misleading test comments about YAML parsing behavior

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

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Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>
Co-authored-by: Peli de Halleux <pelikhan@users.noreply.github.com>

Author: Copilot