[upstream-sync] Target state ownership transfer between components (upstream PR #1787)

[github-actions]

Upstream Change Summary

Type: architectural-change
Difficulty: Hard
Recommendation: Adopt

Upstream PR #1787 introduces target state ownership transfer between components — enabling one component to "take over" a target state path from another via an update operation rather than a delete + re-insert. This restructures pre_commit into two phases and adds inverted tracking (TargetStateOwnerInfo) that maps each TargetStatePath to its owning component.

This is a meaningful correctness improvement: without it, transferring target state ownership between components causes a disruptive delete + insert cycle rather than an in-place update, which can break downstream consistency and is unnecessarily expensive.

Upstream References

• PR: feat: target state ownership transfer between components cocoindex-io/cocoindex#1787
• Upstream repo: https://github.com/cocoindex-io/cocoindex

Relevant Upstream Files / Areas

• rust/core/src/engine/context.rs → crates/recoco-core/src/execution/ (context)
• rust/core/src/engine/execution.rs → crates/recoco-core/src/execution/ (execution engine)
• rust/core/src/state/db_schema.rs → crates/recoco-core/src/execution/ (state tracking)
• python/tests/core/test_ownership_transfer.py → Rust integration tests to be written

Recoco Considerations

• Affected modules: crates/recoco-core execution engine and state tracking
• Key structural changes needed:
  • Add TargetStateOwnerInfo inverted tracking map (maps TargetStatePath → owning component)
  • Restructure pre_commit into two phases:
    • Phase 1: Process inserts/updates; preempt ownership from other components via inverted tracking
    • Phase 2: Handle deletes/contained entries for remaining tracked entries
  • Rename DeclaredEffect → DeclaredTargetState and effect_items → target_state_items
• Performance: The inverted tracking adds memory overhead but eliminates unnecessary delete+insert round-trips; net positive for execution efficiency
• Feature-gating: No new ops — applies to all target types, no new feature gate needed
• API surface: The DeclaredTargetState rename may surface in the public API if these types are exported

Integration Notes

The rename DeclaredEffect → DeclaredTargetState is a breaking change to any internal API using that type. Check recoco's current naming conventions against upstream before adopting. The two-phase pre_commit restructure is the most complex part — requires careful review of execution.rs to ensure recoco's state management remains consistent.