Fix JSON Patch move and copy array targets

[gaoflow]

Summary

• apply the existing JSON Patch add target semantics to move and copy operations
• support the - array target for appending moved or copied values
• reject target indexes greater than the array length instead of silently appending them

Problem

RFC 6902 defines move as a removal followed by add, and copy as add using the source value. The implementation handled their destinations separately with list.insert(), bypassing the boundary behavior fixed for add in #118. As a result, an array target ending in - leaked a native ValueError, while an index greater than the array length was silently clamped to the end by Python.

Delegating the destination step to OpAdd keeps these three standard operations on one target implementation while preserving the deep copy required by copy.

Testing

• 2828 passed, 1 skipped
• ruff check .
• mypy (86 source files)

[jg-rp]

Thanks @gaoflow,

I've refactored it a little to avoid the extra OpAdd instantiation, favoring a standalone private _add() function that OpAdd, OpMove and OpCopy use.

We should probably do a similar thing with a _remove() function in a future PR.