Fix collection for remote UPath nodes

[tobiasraabe]

Summary

• preserve full URIs for non-local UPath values instead of routing them through local path shortening
• exclude non-local path nodes from the collect --nodes common-ancestor calculation
• add regression coverage for remote PickleNode collection and node display

Repro

A task or catalog entry with PickleNode(path=UPath("s3://bucket/in.pkl")) and an empty name would route through local path handling during collection. That produced incorrect names such as s3:/bucket/in.pkl, and collect --nodes could fail when remote UPaths were mixed into the common-ancestor calculation.

Validation

• uv run --python 3.14 --group test pytest tests/test_collect.py tests/test_collect_command.py tests/test_path.py
• uv run --with ruff ruff check src/_pytask/path.py src/_pytask/collect_command.py tests/test_collect.py tests/test_collect_command.py tests/test_path.py
• uv run --group typing --group test --isolated ty check src/_pytask/path.py src/_pytask/collect_command.py tests/test_collect.py tests/test_collect_command.py tests/test_path.py