refactor(actions): emit inherent subtree moves and suppress redundant scaffolding

[HarshK97]

Problem

1. Whenever a node moved in chawathe.go, we were walking all its descendants and creating individual Move actions for every single child and grandchild in that subtree. Then in collapsing.go, we tried to reconstruct whether all those children moved together to collapse them back into a single subtree move. This was fragile and broke anytime a child inside a moved block was deleted or modified, which caused the parent move to get killed and left a bunch of messy orphan moves behind.
2. Scaffolding containers like statement_list, declaration_list, and block were emitting separate Delete and Move actions even when their parent container was already deleted or moved.
3. On a single line, outer wrappers like expression_statement were emitting redundant actions alongside inner child expressions (like selector_expression or call_expression) because we were only checking one level up instead of checking the whole single-line parent chain.
4. In TopDown matching, when multiple identical isomorphic subtrees were candidates (like repeated helper calls or data fields), tie-breakers only checked identifier names and parent Dice score. If neither broke the tie, subtrees could match across completely unrelated sections of the file instead of staying within their local context.

What Changed

• Dropped addDescendantMoves in chawathe.go so parent Move actions are marked with Subtree: len(children) > 0 directly, instead of spamming individual child moves and trying to stitch them back together later.
• Removed the bottom-up move collapsing loop in collapsing.go since moves are now inherently subtree-scoped from the generator.
• Added a second pass (suppressRedundantScaffolding) to drop redundant scaffolding Insert, Delete, and Move actions when their parent container is already doing the work.
• Updated suppressInlineParentRedundancy to walk up single-line ancestors so wrapper expressions on the same line get pruned cleanly.
• Cleaned up collapsing.go by removing the unused contentMoveSuppressed map and deduplicating the scaffolding suppression passes.
• Added parentLineageSimilarity to TopDown matching to score immediate parent and grandparent node type equality as a tie-breaker, keeping identical subtrees matched to their local peers.
• Updated AncestorNameSimilarity to collect pair keys from ancestor pairs and scaffolding containers, improving contextual matching in structured data (JSON, YAML, and map literals).
• Added unit tests in collapsing_test.go and utils_test.go covering scaffolding suppression, multi-level inline pruning, and pair key similarity, and updated golden test fixtures across languages.

Visual Comparison:

c_redis_quadratic_search

Before

After