fix: call onCircular callback for all occurrences of circular $refs

[HugoHSun]

Summary

Fixes #407

The onCircular callback was only invoked for the first detection of each unique circular reference target, not for every occurrence. This was an unintended side effect of the caching optimizations in #380 and #381.

Changes

• Added foundCircularReference(path, $refs, options) calls before returning cached circular results in lib/dereference.ts
• Updated circular-extensive tests to verify correct callback counts (118 paths with circular: true, 173 with circular: 'ignore')
• Added new circular-multi-occurrence test specifically targeting the multiple occurrence scenario

Notes

• The performance optimization from fix(BREAKING CHANGE): dereference caching to prevent infinite loops on circular schemas #380 is preserved - circular refs are still cached
• This matches the behavior of onDereference which correctly fires for every $ref
• The difference in path counts between circular: true (118) and circular: 'ignore' (173) is expected due to traversal behavior differences (documented in tests)

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Pull Request Test Coverage Report for Build 21308961385

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Details

• 2 of 2 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.02%) to 86.441%

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Totals
Change from base Build 21308896778:	0.02%
Covered Lines:	955
Relevant Lines:	1070

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💛 - Coveralls

[github-actions]

🎉 This PR is included in version 15.2.2 🎉

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