Fix docs deploy failing to push gh-pages on every release

[collerek]

The MkDocs/mike docs deploy has failed on every release since 0.21.0. The checkout is shallow and only fetches the pushed tag, so the origin/gh-pages remote-tracking ref never exists locally. mike's update_from_upstream() then no-ops, mike commits an orphan gh-pages, and the push is rejected as a non-fast-forward (! [rejected] gh-pages -> gh-pages (fetch first)).

Fetch gh-pages into the remote-tracking ref before mike deploy so it bases the new commit on the current docs and fast-forwards. Also adds a concurrency group to serialize deploys and replaces the invalid workflow_dispatch: tags: filter with a version input.

Takes effect for releases tagged after this merges; 0.26.0's docs (which never published) can then be deployed via Run workflow with version 0.26.0.

[codspeed-hq]

Merging this PR will improve performance by 15.25%

⚡ 2 improved benchmarks
✅ 96 untouched benchmarks

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚡	WallTime	test_updating_models_individually[20]	165.6 ms	137.8 ms	+20.21%
⚡	WallTime	test_get_column_name_from_alias[1000]	3.4 ms	3.1 ms	+10.5%

Tip

Curious why this is faster? Comment @codspeedbot explain why this is faster on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing fix/docs-deploy-gh-pages (259566b) with master (a7e7fde)}