Reuse ValueIndexPair definition when declaring ValueStringHashes

[staging-devin-ai-integration]

Reuse ValueIndexPair definition when declaring ValueStringHashes

Summary

ValueStringHashes was declaring its second element as std::vector<std::pair<std::size_t, std::size_t>>, which is exactly what ValueIndexPair already defines (line 107 of the same file). This PR replaces the redundant inline type with the existing ValueIndexPair alias.

The resolved type is identical — this is a zero-behavior-change refactor.

Review & Testing Checklist for Human

• Confirm that ValueIndexPair (defined as std::pair<std::size_t, std::size_t> on line 107) is indeed the correct semantic match for the second vector element in ValueStringHashes

Notes

• Build passes cleanly with make configure compile; no formatting diffs remain after make
• Requested by: bot_apk
• Devin Session

[staging-devin-ai-integration]

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