fix: pin adlfs for azure public ingest regression

[ryannikolaidis]

adlfs changed in 2026.4.0 with a breaking auth change: the default anon behavior flipped to False, so code that previously hit public Azure blobs anonymously now tries DefaultAzureCredential unless anon=True is set explicitly. that matches the CI failure here.

this pins adlfs==2026.2.0 to temporarily unblock failing changes when bumping to latest

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Note

Medium Risk
Pins adlfs to an older version to work around an Azure public-container ingest regression, which can affect Azure connector behavior at runtime. The rest is CI-only fixture update plumbing and is low risk.

Overview
Pins adlfs to ==2026.2.0 via pyproject.toml UV constraints (and updates uv.lock) to avoid a regression affecting anonymous access to public Azure blob containers.

Updates the ingest-test-fixtures-update-pr GitHub Actions workflow to also generate and include expected-structured-output-markdown fixtures in the auto-created PRs, and records this change in the CHANGELOG.md.

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