feat(solidlsp): add Astro language server support (#2085)

* feat(solidlsp): add Astro language server support (T170)

* test(solidlsp): fix relative_paths type extraction in test_astro_basic

* refactor(solidlsp): replace asserts with explicit exceptions in Astro LSP

* docs(memories): document rule against assert in language server guide

* docs: add Astro language server documentation (README, docs, template, CHANGELOG)

* feat(solidlsp): implement dual-server architecture for Astro with companion TypeScript server (#2085)

- Implement companion AstroTypeScriptServer using @astrojs/ts-plugin for cross-file code intelligence between .ts and .astro components
- Route .ts/.js document symbols, definitions, references, and renames through companion TypeScript server
- Support two-way buffer edit forwarding between Astro LS and companion TS server
- Replace all assert statements with explicit SolidLSPException and FileNotFoundError
- Handle *.customData configuration requests for Volar HTML service
- Register .astro extension in src/serena/hooks.py
- Add test fixtures and tests for symbol retrieval and cross-file references from TypeScript to Astro components
- Update documentation and CHANGELOG

* fix(solidlsp): narrow astro_ls type to AstroLanguageServer in companion server test

* fix(solidlsp): prevent caching empty document symbols and poll initial compilation in Nextflow tests

pyproject.toml

@@ -386,6 +386,7 @@ markers = [
   "qml: language server running for QML (uses Qt's qmlls)",
   "gleam: language server running for Gleam (uses the Gleam compiler's bundled `gleam lsp`)",
   "wolfram: language server running for Wolfram Language (requires Mathematica 13.0+ or Wolfram Engine 12.1+)",
+  "astro: language server running for Astro (uses @astrojs/language-server)",
 ]
 
 [tool.codespell]