feat(lsp): add config-driven LSP support (Roblox Luau via luau-lsp)

Add Language Server Protocol integration modeled on opencode's, wired for
this codebase's plain-TypeScript tool/agent architecture.

Core (@dispatch/core):
- lsp/client.ts: LSP/JSON-RPC client over stdio (vscode-jsonrpc) with the
  initialize handshake, didOpen/didChange sync, push + pull diagnostics
  (textDocument/diagnostic, workspace/diagnostic), and a generic request()
  passthrough for hover/definition/references/documentSymbol.
- lsp/server.ts: resolves dispatch.toml [lsp] entries into spawn specs.
  Config-driven only — no builtin registry, no auto-download.
- lsp/manager.ts: process-wide LspManager owning client lifecycles, keyed
  by root+serverID, lazy spawn + reuse + graceful shutdown.
- lsp/language.ts: extension->languageId map incl. .luau -> "luau".
- lsp/diagnostic.ts: error-only <diagnostics> block formatting (1-based).
- tools/lsp.ts: on-demand 'lsp' tool (1-based coords -> 0-based wire).
- write-file.ts: optional onAfterWrite hook for diagnostics-on-write.
- config schema: validate [lsp] block; DispatchConfig.lsp + LspServerConfig.

API (@dispatch/api):
- AgentManager owns one LspManager; per-working-directory server cache
  cleared on config reload; diagnostics appended to write_file results;
  'lsp' tool gated by new perm_lsp setting; shutdownAll on destroy().

Config:
- dispatch.toml: documented, commented [lsp.luau-lsp] Roblox example.

Tests: fake-lsp-server fixture + client/manager/server/diagnostic/schema/
tool/write-hook suites, plus an opt-in real-binary luau-lsp smoke test
(auto-skipped when luau-lsp is absent). 652 pass; biome + 3 typechecks green.

1 files changed, 42 insertions, 0 deletions

diff --git a/dispatch.toml b/dispatch.toml
index 43e164a..9f09ef7 100644
--- a/dispatch.toml
+++ b/dispatch.toml
@@ -49,3 +49,45 @@ read = "allow"
 [permissions.external_directory]
 "~/*" = "ask"
 "/tmp/*" = "allow"
+
+# ─── Language Servers (LSP) ──────────────────────────────────────
+# Optional. Declare LSP servers to give agents diagnostics (and, with the
+# `lsp` tool, hover/definition/references) for the files they edit. This block
+# is PROJECT-SCOPED: it is read from the `dispatch.toml` in a tab's effective
+# working directory (re-consulted when you change the CWD). Config-driven only —
+# there is no builtin server registry and no auto-download, so the executable
+# in `command[0]` must already be on PATH.
+#
+# After `write_file` edits a file whose extension matches a server below,
+# dispatch opens it through the server and appends any error diagnostics to the
+# tool result ("LSP errors detected in this file, please fix: ..."). Grant the
+# `perm_lsp` permission to also expose the on-demand `lsp` tool.
+#
+# The example below is the Roblox Luau setup using luau-lsp
+# (https://github.com/JohnnyMorganz/luau-lsp). Uncomment and adapt for your
+# project. luau-lsp's `sourcemap.autogenerate` makes luau-lsp run
+# `rojo sourcemap --watch` itself, so `rojo` must be on PATH (or set
+# `[lsp.luau-lsp.env]` PATH / luau-lsp's sourcemap.rojoPath accordingly).
+#
+# [lsp.luau-lsp]
+# command = ["luau-lsp", "lsp", "--definitions=globalTypes.d.luau", "--docs=api-docs.json"]
+# extensions = [".luau"]
+#
+# [lsp.luau-lsp.initialization.luau-lsp.platform]
+# type = "roblox"
+#
+# [lsp.luau-lsp.initialization.luau-lsp.sourcemap]
+# enabled = true
+# autogenerate = true
+# rojoProjectFile = "default.project.json"
+#
+# [lsp.luau-lsp.initialization.luau-lsp.types]
+# roblox = true
+# definitionFiles = ["globalTypes.d.luau"]
+# documentationFiles = ["api-docs.json"]
+#
+# [lsp.luau-lsp.initialization.luau-lsp.diagnostics]
+# strictDatamodelTypes = false
+#
+# [lsp.luau-lsp.initialization.luau-lsp.completion.imports]
+# useConst = true