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.

2 files changed, 60 insertions, 0 deletions

diff --git a/packages/api/tests/agent-manager.test.ts b/packages/api/tests/agent-manager.test.ts
index 3353aff..6efe15e 100644
--- a/packages/api/tests/agent-manager.test.ts
+++ b/packages/api/tests/agent-manager.test.ts
@@ -228,6 +228,36 @@ vi.mock("@dispatch/core", () => ({
 			execute: async () => ["file1.ts"],
 		};
 	},
+	createLspTool(_getContext: unknown): ToolDefinition {
+		return {
+			name: "lsp",
+			description: "query the language server",
+			parameters: { _type: "z.ZodObject", shape: {} } as unknown as ToolDefinition["parameters"],
+			execute: async () => "mock lsp",
+		};
+	},
+	LspManager: class MockLspManager {
+		hasServerForFile() {
+			return false;
+		}
+		async getClients() {
+			return [];
+		}
+		async touchFile() {}
+		getDiagnostics() {
+			return {};
+		}
+		async request() {
+			return [];
+		}
+		async shutdownAll() {}
+	},
+	resolveServersFromConfig(_lsp: unknown) {
+		return [];
+	},
+	reportDiagnostics(_file: string, _issues: unknown) {
+		return "";
+	},
 	createRunShellTool(_wd: string): ToolDefinition {
 		return {
 			name: "run_shell",
diff --git a/packages/api/tests/routes.test.ts b/packages/api/tests/routes.test.ts
index a8db5ce..6ec8ca6 100644
--- a/packages/api/tests/routes.test.ts
+++ b/packages/api/tests/routes.test.ts
@@ -82,6 +82,36 @@ vi.mock("@dispatch/core", () => ({
 			execute: async () => ["file1.ts"],
 		};
 	},
+	createLspTool(_getContext: unknown): ToolDefinition {
+		return {
+			name: "lsp",
+			description: "query the language server",
+			parameters: { _type: "z.ZodObject", shape: {} } as unknown as ToolDefinition["parameters"],
+			execute: async () => "mock lsp",
+		};
+	},
+	LspManager: class MockLspManager {
+		hasServerForFile() {
+			return false;
+		}
+		async getClients() {
+			return [];
+		}
+		async touchFile() {}
+		getDiagnostics() {
+			return {};
+		}
+		async request() {
+			return [];
+		}
+		async shutdownAll() {}
+	},
+	resolveServersFromConfig(_lsp: unknown) {
+		return [];
+	},
+	reportDiagnostics(_file: string, _issues: unknown) {
+		return "";
+	},
 	createRunShellTool(_wd: string): ToolDefinition {
 		return {
 			name: "run_shell",