feat: port CLI, TUI, and launcher from v1.5 into v2 (#1452)

Ports the CLI, TUI, and launcher from v1.5 into v2 behind a single
`mcp-inspector` entrypoint (launcher → web/cli/tui). Includes the
`mcp-inspector --web --dev` launcher fix (Vite alias resolution + prod-server
double-start), the root `postinstall` install cascade with simplified CI, and
spec/AGENTS docs (no-workspaces rationale, Development setup).

Closes #1246.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

clients/launcher/__tests__/parse-launcher-argv.test.ts

@@ -0,0 +1,50 @@
+import { describe, expect, it } from "vitest";
+import { parseLauncherArgv } from "../src/parse-launcher-argv.js";
+
+const EXEC = ["node", "/path/to/launcher/build/index.js"];
+
+describe("parseLauncherArgv", () => {
+  it("defaults to web when no mode flag is in the prefix", () => {
+    expect(parseLauncherArgv([...EXEC, "--method", "tools/list"])).toEqual({
+      mode: "web",
+      forwardedArgv: [...EXEC, "--method", "tools/list"],
+      hasPrefixModeFlag: false,
+    });
+  });
+
+  it("selects mode from a leading mode flag and strips only the prefix", () => {
+    expect(
+      parseLauncherArgv([...EXEC, "--cli", "node", "./server.js", "--cli"]),
+    ).toEqual({
+      mode: "cli",
+      forwardedArgv: [...EXEC, "node", "./server.js", "--cli"],
+      hasPrefixModeFlag: true,
+    });
+  });
+
+  it("does not treat a trailing mode-like token as launcher mode", () => {
+    expect(parseLauncherArgv([...EXEC, "node", "./server.js", "--cli"])).toEqual(
+      {
+        mode: "web",
+        forwardedArgv: [...EXEC, "node", "./server.js", "--cli"],
+        hasPrefixModeFlag: false,
+      },
+    );
+  });
+
+  it("rejects multiple mode flags in the launcher prefix", () => {
+    expect(() => parseLauncherArgv([...EXEC, "--cli", "--tui"])).toThrow(
+      /at most one of --web, --cli, or --tui/,
+    );
+  });
+
+  it("forwards a later mode-like token after non-mode app args", () => {
+    expect(
+      parseLauncherArgv([...EXEC, "--tui", "--config", "x", "--cli"]),
+    ).toEqual({
+      mode: "tui",
+      forwardedArgv: [...EXEC, "--config", "x", "--cli"],
+      hasPrefixModeFlag: true,
+    });
+  });
+});