fix(delete): preserve parent type for non-empty subtree deletes

[QuantumExplorer]

Summary

• reuse the already-open parent Merk when deleting a non-empty child tree
• keep delete propagation using the parent tree type instead of reopening with the child tree type
• add CountTree and CountSumTree regressions that delete populated child trees and verify aggregates

Fixes #686.

Verification

• cargo test -p grovedb non_empty_tree_delete_under --lib
• cargo test -p grovedb test_recurring_deletion_through_subtrees --lib

Summary by CodeRabbit

• New Features

  • Delete operation support enabled for GroveDB v3 protocol.

• Improvements

  • Enhanced error handling and messages for delete operations.

• Tests

  • Added comprehensive test coverage for delete operations across protocol versions, including backward compatibility validation.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: dd897149-e228-4f44-8b24-1338d8ba4769

📥 Commits

Reviewing files that changed from the base of the PR and between a2129a9 and 38944e8.

📒 Files selected for processing (2)

• grovedb-version/src/version/v3.rs
• grovedb/src/operations/delete/mod.rs

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📝 Walkthrough

Walkthrough

This PR enables delete_internal_on_transaction for GroveDB v3 and fixes a critical bug where non-empty tree deletion under aggregate parents (CountTree, sum, count-sum) could reopen the parent using the child's tree type instead of the parent's, corrupting counter/sum metadata. The implementation introduces version-dependent logic with a legacy v0 path and modern v1+ path, ensuring consistent use of parent tree type throughout.

Changes

Delete operation v1 versioning and aggregation fix

Layer / File(s)	Summary
Version flag configuration grovedb-version/src/version/v3.rs	GROVE_V3 protocol version enables delete_internal_on_transaction operation by updating its version flag from 0 to 1.
Version check infrastructure and error handling grovedb/src/operations/delete/mod.rs	Imports check_grovedb_v0_or_v1_with_cost function, adds cannot_open_subtree_with_root_key_error helper to convert subtree opening failures into Error::CorruptedData, and switches delete_internal_on_transaction version gate macro from v0-only to v0-or-v1 checking.
Version-dependent deletion with parent tree type grovedb/src/operations/delete/mod.rs	Introduces parent_tree_type variable saved from parent subtree. Reworks non-empty tree deletion into version-dependent branches: v0 legacy path reopens parent storage using subtree root key (with error mapping) then performs sectioned deletion; v1+ path deletes directly on already-open transactional merk. Both paths consistently use parent_tree_type when calling Element::delete_with_sectioned_removal_bytes.
Error mapping and aggregate parent deletion tests grovedb/src/operations/delete/mod.rs	Imports GROVE_V2 for legacy tests. Adds test_open_subtree_root_key_error_mapping to verify error conversion. Adds comprehensive tests deleting non-empty children under count/count-sum aggregate parents, verifying parent counter/sum metadata decreases correctly, verify_grovedb returns no issues, and a GROVE_V2 compatibility test ensures legacy v0 deletion path behavior is preserved.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Poem

🐰 A rabbit hops through versions true,
Where v0 paths meet v1 anew.
Parent trees stay pure and bright,
Aggregate counts held ever tight.
Delete flows smooth, both old and new! 🌳

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: fixing delete operations to preserve parent type when handling non-empty subtree deletes.
Linked Issues check	✅ Passed	The PR addresses issue #686 by implementing version-dependent delete behavior: v0 uses legacy reopening (child type) for backward compatibility, v1 reuses open parent Merk (parent type), with comprehensive test coverage for CountTree/CountSumTree aggregate propagation.
Out of Scope Changes check	✅ Passed	All changes are in-scope: version flag update for v3 support, delete operation logic refactoring with version dispatching, helper function for error mapping, and targeted test additions for aggregate validation.
Docstring Coverage	✅ Passed	Docstring coverage is 88.89% which is sufficient. The required threshold is 80.00%.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch codex/fix-686-delete-parent-tree-type

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.47%. Comparing base (60f2968) to head (38944e8).
⚠️ Report is 3 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #732      +/-   ##
===========================================
+ Coverage    91.42%   91.47%   +0.04%     
===========================================
  Files          236      236              
  Lines        67053    67321     +268     
===========================================
+ Hits         61305    61580     +275     
+ Misses        5748     5741       -7     

Components	Coverage Δ
grovedb-core	89.06% <100.00%> (+0.11%)	⬆️
merk	92.25% <ø> (-0.02%)	⬇️
storage	86.36% <ø> (ø)
commitment-tree	96.43% <ø> (ø)
mmr	96.79% <ø> (+0.03%)	⬆️
bulk-append-tree	89.39% <ø> (+0.13%)	⬆️
element	97.38% <ø> (+0.01%)	⬆️

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[QuantumExplorer]

Reviewed