[upstream-sync] feat(splitter): add Astro tree-sitter language support (upstream #1984)

[github-actions]

Upstream Change Summary

Type: new-feature
Difficulty: Easy
Recommendation: Adopt

Upstream wired tree-sitter-astro-next (v0.1.1) into the astro language entry in prog_langs.rs, replacing a separator-only fallback with full syntax-aware splitting for .astro files. This directly maps to crates/recoco-splitters, where the same grammar can be added under the existing language-detection and splitting infrastructure.

Upstream References

• PR: feat(splitter): add Astro tree-sitter support cocoindex-io/cocoindex#1984
• Upstream repo: https://github.com/cocoindex-io/cocoindex

Relevant Upstream Files / Areas

• rust/ops_text/src/prog_langs.rs — wires tree-sitter-astro-next into the astro language entry
• rust/ops_text/Cargo.toml — adds tree-sitter-astro-next = "0.1.1" (tree-sitter ^0.25.10)

Recoco Considerations

• Affected files: crates/recoco-splitters/src/prog_langs.rs, crates/recoco-splitters/Cargo.toml
• Feature-gating: No new feature gate needed — tree-sitter grammars are unconditionally included in the splitters crate as part of core splitting functionality
• Dependency version: Verify tree-sitter-astro-next 0.1.1 is compatible with recoco-splitters' current tree-sitter version (should match ^0.25.10)
• No Python code to exclude

Integration Notes

Straightforward port following the same pattern as recent Elm and Julia additions. Add the astro grammar entry to prog_langs.rs, add the crate dependency to Cargo.toml. Port the upstream unit tests: test_astro_has_treesitter (extension detection) and a round-trip splitting test for Astro content.