refactor(version): single-source the version from the root package.json

The Inspector ships as one package with one version, but four client
package.jsons each carried their own `version` and were read at runtime
(cli.ts, tui App.tsx), and core hardcoded a third, stale value (0.20.0) that
the TUI and web actually reported to servers. Consolidate onto the root
package.json as the single source of truth.

- Add core/node/version.ts: shared, Node-only readInspectorVersion() that walks
  up to the root package.json (always shipped in the tarball). 100% covered by a
  new integration test.
- CLI and TUI read the version via the shared reader instead of their own
  manifest; TUI now also passes a real clientIdentity (was falling through to
  the stale core default).
- Drop the `version` field from all four client package.jsons; the root keeps
  the only version. TUI header name/description become local display constants.
- core default client identity: replace the stale 0.20.0 hardcode with a neutral
  0.0.0 placeholder (real clients pass clientIdentity; web will source its
  version from GET /api/config, see #1639).
- Stop shipping clients/cli/package.json and clients/tui/package.json (no longer
  read at runtime) — supersedes the earlier "ship them" fix; update pack:verify
  and the root README packaging invariants accordingly.
- Add core/node/** to the web coverage include so the new module is gated.
- Add the shared-code architecture diagram to the root README.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BrihGWcrM9JGRyu41nzZYw

core/mcp/inspectorClient.ts

@@ -26,11 +26,16 @@ export type {
   AppRendererClient,
 } from "./types.js";
 import { getServerType as getServerTypeFromConfig } from "./config.js";
-// v2 doesn't have a core/package.json (the package isn't published independently),
-// so we hardcode the client identity that v1.5 read from corePackageJson.
+// Fallback client identity, used ONLY when a caller doesn't pass
+// `clientIdentity`. Real clients supply their own: the Node clients (CLI, TUI)
+// read the single-source version from the root package.json via
+// `readInspectorVersion()`, and the web browser — which can't read the
+// filesystem — will pass a version sourced from `GET /api/config` (see #1639).
+// This stays a neutral placeholder rather than a hardcoded release number that
+// would silently drift out of sync with the root package.json version.
 const corePackageJson = {
-  name: "@modelcontextprotocol/inspector-core",
-  version: "0.20.0",
+  name: "mcp-inspector",
+  version: "0.0.0",
 } as const;
 import type {
   CreateTransport,