[M10] Implement LSP server as a thin protocol adapter

[Teakowa]

Parent: #27

Depends on: #63, #65, #66

Planning status: settled by the #75 contract — true in-flight cancellation is
deferred; stale-result suppression is the M10 requirement.

Goal

Expose Wright's editor-neutral language services through standard LSP without making LSP protocol types or lifecycle the compiler architecture.

Scope

• Implement LSP initialize/capability negotiation and document/workspace lifecycle mapping.
• Map diagnostics, hover, definition, references, completion, rename, and semantic tokens to the Wright-owned language-service APIs.
• Map document versions, stale-result suppression, errors, and source edits correctly between LSP and core contracts. In-flight request cancellation is explicitly deferred (see [M10 planning] Reconcile cancellation and responsive-analysis contracts #75) and is not an M10 requirement.
• Support stdio as the baseline server transport unless evidence justifies more.
• Keep server state thin over the shared workspace/session model.
• Add protocol-level integration tests using actual LSP messages.

Non-goals

• Shipping VS Code/browser/editor extensions.
• Reimplementing semantic logic in LSP handlers.
• Making LSP DTOs public compiler-core types.
• Introducing speculative in-flight cancellation infrastructure ([M10 planning] Reconcile cancellation and responsive-analysis contracts #75).

Acceptance criteria

• Standard LSP clients can consume the supported Wright language-service capabilities.
• Protocol handlers are thin mappings over editor-neutral services and have no duplicate semantic implementation.
• Version handling prevents stale responses from being applied as current results. This is distinct from in-flight request cancellation, which is explicitly deferred per [M10 planning] Reconcile cancellation and responsive-analysis contracts #75.
• The LSP server can be tested independently through protocol messages.

[Teakowa]

Delivered in commit 7b0d0f2 (crates/wright-lsp).

• A thin LSP adapter over wright_language::LanguageService: stdio Content-Length framing, capability negotiation (hover/definition/references/completion/rename/full semantic tokens), document lifecycle (didOpen/didChange/didClose), versioned publishDiagnostics, hover/definition/references/completion/rename (workspace edit with the validated preview), semanticTokens/full, shutdown/exit.
• No semantic logic in the adapter; the language core contains no LSP types.

[Teakowa]

Remediated and re-verified (commits c4fc954..c8c17b2).

• The LSP adapter remains a thin mapping over wright_language with no semantic logic and no LSP types in the core.
• It now passes through the client textDocument.version, maps source-aware locations to the correct target URI, returns real rename ranges and explicit refusals, resolves the workspace root from initialize, and advertises UTF-16 with matching position conversion.