feat: Forward virtual filesystem documents to language server

note: We have to wait for gitlab-org/editor-extensions/gitlab-lsp!3295 (merged) and update gitlab-lsp version before merging this MR.

Description

Companion to gitlab-org/editor-extensions/gitlab-lsp!3295 (merged).

Adds adt and semanticfs to the LanguageClient documentSelector so documents from virtual FileSystemProviders reach the LSP via textDocument/didOpen. Without this, Duo Agent Platform actions on those documents fail with "Active editor document cannot be retrieved by URL".

Related Issues

Resolves gitlab-org/editor-extensions/gitlab-lsp#2128 (with the companion LSP MR).

Follow-ups

• #2277 — Add gitlab.virtualWorkspaceProjects setting for pure-virtual-workspace users
• gitlab-org/editor-extensions/gitlab-lsp#2364 — Route list_dir and find_files over a custom LSP request for virtual workspaces (LSP-side)
• gitlab-org/editor-extensions/gitlab-lsp#2365 — Webview's isDuoEnabledForAnyProject ignores LSP defaultNamespace fallback (LSP-side)
• gitlab-org/editor-extensions/gitlab-lsp#2366 — Audit fsPath / workspaceFolderPathFromUri callsites for virtual-workspace gaps (LSP-side)

How has this been tested?

Local end-to-end against a minimal testfs:// FileSystemProvider extension with the LSP MR applied: opening a virtual file delivers the document to the LSP store and Duo Agent Platform read_file and edit_file actions succeed.

• If src/browser or src/common has been modified, please consider interoperability with the Web IDE. Reviewed: the change is purely additive to the existing scheme list (Web IDE already uses gitlab-web-ide from the same array) so it cannot regress Web IDE behaviour.
• Consider an end-to-end test for significant new features.

Screenshots (if appropriate)

N/A — no UI change.

What CHANGELOG entry will this MR create?

• fix: Bug fix
• feature: New feature
• BREAKING CHANGE:
• None - other non-user-facing changes