fix: deep-copy source attributes in from_array

[d-v-b]

This AI-authored PR ensures that from_array copies source array attributes by value instead of by reference, which prevents mutating the input attributes as a side effect of mutating the derived array's attributes.

🤖 AI text below 🤖

Summary

zarr.from_array (since #4288) copies the source array's attributes onto the new array with dict(data.attrs), which is a shallow copy. Any nested dict or list inside the attributes was therefore shared between the source array's in-memory metadata and the new array's, so mutating a nested attribute on the copy — for example dst.attrs["meta"]["tags"].append(...) — silently changed the source array's attributes too. The alias never reached the source's store, but it was created by zarr without the user's involvement, which is a surprise.

This PR switches to copy.deepcopy; attributes are JSON values (dicts, lists, scalars), so the deep copy is safe and cheap. The existing from_array attribute test now mutates a nested dict and a nested list on the copy and asserts the source is unchanged; it fails on main and passes here.

Found during the pre-release review for #4256.

For reviewers

The source change is a one-liner plus an import copy. fill_value was checked for the same issue and does not have it: the value is re-parsed when the new array's metadata is built, so even structured np.void fill values are distinct objects between source and copy.

Author attestation

• I am a human, these are my changes, and I have reviewed and understood every change and can explain why each is correct.

TODO

• Add unit tests and/or doctests in docstrings
• Add docstrings and API docs for any new/modified user-facing classes and functions (n/a)
• New/modified features documented in docs/user-guide/*.md (n/a)
• Changes documented as a new file in changes/
• GitHub Actions have all passed
• Test coverage is 100% (Codecov passes)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.31%. Comparing base (db93545) to head (c906c8e).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4325   +/-   ##
=======================================
  Coverage   94.31%   94.31%           
=======================================
  Files          92       92           
  Lines       12919    12920    +1     
=======================================
+ Hits        12184    12185    +1     
  Misses        735      735           

Files with missing lines	Coverage Δ
src/zarr/core/array.py	98.08% <100.00%> (+<0.01%)	⬆️

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