fix: compatibility with pandas 3.0 for string coords

[aseyboldt]

Fixes an issue with the recent pandas 3.0 release:

RuntimeError: Coordinate unconstrained_parameter value has unsupported type

Caused by:
    RuntimeError: Could not convert to Value. Unsupported type: ArrowStringArray

Also Closes #270

[Copilot]

Pull request overview

Updates nutpie to handle pandas 3.0’s Arrow-backed string coordinates (avoiding ArrowStringArray conversion failures) and expands CI/release support for Python 3.14.

Changes:

• Add ArrowStringArray handling in Rust ↔ Python value conversion to support pandas 3.0 string coords.
• Loosen a datetime64 dtype assertion in PyMC zarr tests to accommodate pandas 3.0 precision changes.
• Bump several Rust dependencies and extend CI matrices/build arguments to include Python 3.14 (plus macOS runner adjustments).

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/common.rs	Adds conversion path for pandas ArrowStringArray into Value::Strings.
tests/test_pymc.py	Updates datetime64 dtype assertions to accept pandas 3.0 precision changes.
Cargo.toml	Updates Rust dependency versions (incl. object store / zarr-related crates, criterion, tch).
Cargo.lock	Lockfile refresh reflecting dependency upgrades.
.github/workflows/ci.yml	Adds Python 3.14 to CI/builds, updates macOS runner, and conditionally skips some macOS x86_64 tests.

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