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, 110 insertions, 0 deletions

diff --git a/packages/core/tests/config/lsp-schema.test.ts b/packages/core/tests/config/lsp-schema.test.ts
new file mode 100644
index 0000000..2b71cc2
--- /dev/null
+++ b/packages/core/tests/config/lsp-schema.test.ts
@@ -0,0 +1,110 @@
+import { describe, expect, it } from "vitest";
+import { validateConfig } from "../../src/config/schema.js";
+
+describe("config schema — [lsp] block", () => {
+	it("parses a valid custom server entry", () => {
+		const { config, errors } = validateConfig({
+			permissions: {},
+			lsp: {
+				"luau-lsp": {
+					command: ["luau-lsp", "lsp"],
+					extensions: [".luau"],
+					initialization: { "luau-lsp": { platform: { type: "roblox" } } },
+				},
+			},
+		});
+		expect(errors).toHaveLength(0);
+		expect(config.lsp).toBeDefined();
+		const entry = config.lsp?.["luau-lsp"];
+		expect(entry?.command).toEqual(["luau-lsp", "lsp"]);
+		expect(entry?.extensions).toEqual([".luau"]);
+		expect(entry?.initialization).toEqual({
+			"luau-lsp": { platform: { type: "roblox" } },
+		});
+	});
+
+	it("preserves env and nested initialization verbatim", () => {
+		const { config } = validateConfig({
+			permissions: {},
+			lsp: {
+				"luau-lsp": {
+					command: ["luau-lsp", "lsp"],
+					extensions: [".luau"],
+					env: { PATH: "/custom/bin" },
+					initialization: {
+						"luau-lsp": {
+							sourcemap: { enabled: true, autogenerate: true },
+							diagnostics: { strictDatamodelTypes: false },
+						},
+					},
+				},
+			},
+		});
+		const entry = config.lsp?.["luau-lsp"];
+		expect(entry?.env).toEqual({ PATH: "/custom/bin" });
+		expect(entry?.initialization).toEqual({
+			"luau-lsp": {
+				sourcemap: { enabled: true, autogenerate: true },
+				diagnostics: { strictDatamodelTypes: false },
+			},
+		});
+	});
+
+	it("rejects a custom server missing command", () => {
+		const { config, errors } = validateConfig({
+			permissions: {},
+			lsp: { broken: { extensions: [".luau"] } },
+		});
+		expect(errors.some((e) => e.path === "lsp.broken.command")).toBe(true);
+		expect(config.lsp).toBeUndefined();
+	});
+
+	it("rejects a custom server missing extensions", () => {
+		const { errors } = validateConfig({
+			permissions: {},
+			lsp: { broken: { command: ["x"] } },
+		});
+		expect(errors.some((e) => e.path === "lsp.broken.extensions")).toBe(true);
+	});
+
+	it("rejects an empty command array", () => {
+		const { errors } = validateConfig({
+			permissions: {},
+			lsp: { broken: { command: [], extensions: [".luau"] } },
+		});
+		expect(errors.some((e) => e.path === "lsp.broken.command")).toBe(true);
+	});
+
+	it("keeps a disabled entry without requiring command/extensions", () => {
+		const { config, errors } = validateConfig({
+			permissions: {},
+			lsp: { "luau-lsp": { disabled: true } },
+		});
+		expect(errors).toHaveLength(0);
+		expect(config.lsp?.["luau-lsp"]?.disabled).toBe(true);
+	});
+
+	it("skips a malformed entry but keeps valid siblings", () => {
+		const { config, errors } = validateConfig({
+			permissions: {},
+			lsp: {
+				good: { command: ["a"], extensions: [".luau"] },
+				bad: { extensions: [".luau"] },
+			},
+		});
+		expect(config.lsp?.good).toBeDefined();
+		expect(config.lsp?.bad).toBeUndefined();
+		expect(errors.length).toBeGreaterThan(0);
+	});
+
+	it("omits lsp entirely when not present", () => {
+		const { config, errors } = validateConfig({ permissions: {} });
+		expect(errors).toHaveLength(0);
+		expect(config.lsp).toBeUndefined();
+	});
+
+	it("flags a non-object lsp value", () => {
+		const { errors } = validateConfig({ permissions: {}, lsp: "nope" });
+		expect(errors.some((e) => e.path === "lsp")).toBe(true);
+	});
+});