feat(compiler): auto-generate reference url and surface docs on hover

[tadelesh]

Follow-up to #11221 (stacked on top of it). Builds on the tspd documentation generation to make the same docs available in the editor.

Note

Base is tadelesh/auto-gen-rule-diagnostic-docs (#11221). Review/merge that first; this PR's diff is just the url + hover delta.

Compiler

• Auto-generated reference url. The library definition passed to createTypeSpecLibrary accepts referenceDocs.baseUrl. When set, the compiler auto-fills the url of any documented diagnostic/rule that does not specify one:

  • diagnostics -> ${baseUrl}/diagnostics/<code>
  • linter rules -> ${baseUrl}/rules/<name>

  This gives every documented diagnostic/rule a clickable code link in the editor without hardcoding a url per item, while avoiding links to pages that are not generated. An explicit url still takes precedence.

• Language server hover. Hovering over a reported error now renders the extended docs of the corresponding diagnostic/rule as markdown, plus a "See documentation" link when a url is available. The LSP Diagnostic message is plain-text only (there is no markdown field on it), so hover is the only channel that can show rich docs inline at an error. Since emitter/linter diagnostics only exist in the full compile, the hover reuses the diagnostics from the last full compile — matched by source location the same way the squiggles are — and resolves each one's docs through a new @internal Program.getLoadedLibraryInfo that loads the library's default entry via the compiler's own (cached) entrypoint loader. That default entry is where the linter export lives, whereas the entry .tsp files import (the typespec condition) may only expose the library definition.

Pilots

• @typespec/http — the op-reference-container-route rule declares referenceDocs.baseUrl and drops its hardcoded url (now auto-generated).
• @typespec/openapi3 — declares referenceDocs.baseUrl so its 6 documented diagnostics get auto-generated urls.
• Both packages now publish their src/**/*.md so installed libraries can resolve FileRef docs at runtime (used by the hover).

Validation

• Built compiler, http, openapi3; the compiler server suite (including the URL and hover tests) and the op-reference-container-route rule tests pass.