Use fsspec for remote cache downloads

[d-chambers]

Description

Use fsspec/universal-pathlib as the single transport for remote cache materialization.

The HTTP cache fallback previously opened a second urllib connection because materialization could begin while the failed fsspec handle was still open. This duplicated HTTP behavior and required manually translating only a subset of fsspec storage options.

This change closes the failed remote handle before materialization, then streams HTTP resources through UPath.open(..., block_size=0). It removes the urllib-specific header/auth translation and the blocking-download timeout setting that only applied to that alternate stack. The existing atomic cache write and configured download chunk size remain unchanged.

Regression tests verify that HTTP materialization uses the UPath/fsspec transport and that the failed remote handle is closed before the local cache opener runs.

Validation:

• pytest tests -m "not network" -q — 7,735 passed
• pytest tests -m network -q — 100 passed
• pytest dascore --doctest-modules -q — 142 passed
• pre-commit run --all-files — passed

Changelog

none

Checklist

I have (if applicable):

• referenced the GitHub issue this PR closes.
• documented the new feature with docstrings and/or appropriate doc page.
• included tests. See testing guidelines.
• added the "ready_for_review" tag once the PR is ready to be reviewed.

Summary by CodeRabbit

• Bug Fixes
  • Improved remote file downloading across supported HTTP and S3-compatible storage backends.
  • Enhanced fallback handling so remote connections close cleanly when switching to cached local files.
  • Removed the remote download timeout option from runtime configuration; downloads now use the underlying storage connection’s behavior.

[coderabbitai]

📝 Walkthrough

Walkthrough

Changes

Remote download transport

Layer / File(s)	Summary
Resource-based remote download dascore/config.py, dascore/utils/remote_io.py, tests/test_utils/test_io_utils.py	Removes the remote timeout setting and urllib fallback, uses resource.open(...) for all protocols, and updates tests for resource-based streaming and block sizes.
Fallback handle switching dascore/utils/remote_io.py, tests/test_utils/test_io_utils.py	Closes the remote handle before reopening the cached local handle and verifies this behavior while preserving position.

Possibly related PRs

• DASDAE/dascore#741: Directly overlaps with the remote HTTP download fallback and its header/authentication test coverage.

Suggested labels: IO

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title is concise and accurately summarizes the main change to remote cache downloads.
Description check	✅ Passed	The PR description matches the template and includes the required summary, checklist, and validation details.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch agent/fsspec-only-remote-cache

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (2aa3c00) to head (2ee02a6).
⚠️ Report is 1 commits behind head on dev.

Additional details and impacted files

@@            Coverage Diff            @@
##               dev      #758   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          161       161           
  Lines        16619     16587   -32     
=========================================
- Hits         16619     16587   -32     

Flag	Coverage Δ
network	49.65% <100.00%> (-0.01%)	⬇️
unittests	99.98% <100.00%> (-0.01%)	⬇️

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