Guard GraphQL PR number conversion against int32 overflow

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This PR addresses the CodeQL alert on unsafe integer downcast when passing PR numbers into GraphQL query variables. The change ensures int values are validated before converting to graphql.Int (int32-backed).

• What changed

  • Added a narrow conversion helper in internal/github/github.go:
    • toGraphQLInt(n int) (graphql.Int, error)
    • Enforces math.MinInt32 <= n <= math.MaxInt32
  • Updated FindPRByNumber to use the validated conversion instead of direct cast.

• Behavioral impact

  • Out-of-range PR numbers now fail fast with a clear error instead of risking truncation/overflow during conversion.

• Focused coverage

  • Added unit tests in internal/github/github_test.go for:
    • successful in-range conversion
    • error on out-of-range conversion

func toGraphQLInt(n int) (graphql.Int, error) {
	if n < math.MinInt32 || n > math.MaxInt32 {
		return 0, fmt.Errorf("number %d is out of GraphQL Int range", n)
	}
	return graphql.Int(n), nil
}

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Pull request overview

This PR mitigates a CodeQL-reported unsafe integer downcast by validating int PR numbers before converting them into graphql.Int (int32-backed) for GraphQL query variables.

Changes:

• Added toGraphQLInt(n int) (graphql.Int, error) to enforce GraphQL Int range bounds before conversion.
• Updated FindPRByNumber to use the validated conversion instead of a direct cast.
• Added unit tests covering in-range success and out-of-range failure for the new helper.

Show a summary per file

File	Description
internal/github/github.go	Adds the guarded int→graphql.Int conversion helper and uses it in FindPRByNumber.
internal/github/github_test.go	Adds unit tests for toGraphQLInt range validation behavior.

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• Files reviewed: 2/2 changed files
• Comments generated: 0