feat: add mobilewright inspect command with browser-based element inspector

Adds a new `@mobilewright/inspector` workspace package and a `mobilewright inspect`
CLI subcommand that opens a browser-based element inspector for connected devices.

The inspector shows a live screenshot on the left and an annotated element list on the
right. Each element is annotated with the best mobilewright locator (testId > role >
label > text), mirroring the priority order of @mobilewright/core's query engine.
Clicking a locator highlights its bounding box on the screenshot; clicking a box
selects the matching row. Duplicate locators get a "dup" badge.

Architecture:
- packages/inspector: standalone Express server, plain HTML/CSS/JS frontend (no build
  step), locator derivation pure function, DeviceManager with injected launchers (DIP)
- packages/mobilewright: inspect CLI command injects ios/android launchers into start()
  to avoid a circular dependency; open is an explicit dependency here

Hardening and review fixes:
- Logs to stderr so the URL line on stdout is uncluttered
- Port validated as integer in [0, 65535]
- Node 18 compatible server close (no Symbol.asyncDispose)
- 4-arg Express error handler returns JSON on unexpected throws
- escQ escapes backslashes in addition to single quotes
- open() wrapped in try/catch so headless environments print URL and continue
- device.screenSize() replaces PNG IHDR heuristic for correct iPad support
- 404 check in select route matches by id AND platform
- Test files excluded from tsconfig (not shipped in dist)
- Stale screenshot cleared when active device disconnects
- aria-label on device picker and interval selects; vis-btn aria-label kept in sync
- Passes ESLint @stylistic/semi throughout
- 83 tests (@playwright/test): locator derivation, DeviceManager, HTTP routes

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: marcomaes

README.md

@@ -482,6 +482,19 @@ ID                                      Name                     Platform  Type
 5A5FCFCA-27EC-4D1B-B412-BAE629154EE0    iPhone 17 Pro            ios       simulator   booted
 ```
 
+### `mobilewright inspect`
+
+Open the Mobilewright Inspector — a browser-based UI showing a live screenshot of your connected device alongside every element and its best locator.
+
+```bash
+npx mobilewright inspect
+npx mobilewright inspect --port 4621   # use a specific port (default: 4621)
+```
+
+The Inspector opens automatically in your browser. Select a device from the picker at the top, then click **Refresh** or enable **Auto refresh**. Click any row in the element list to highlight its bounding box on the screenshot. Elements that share a locator with another element get a `dup` badge.
+
+Locator priority matches what mobilewright uses: `getByTestId` > `getByRole` > `getByLabel` > `getByText`.
+
 ### `mobilewright screenshot`
 
 Capture a screenshot of a connected device. Auto-starts mobilecli if it isn't running.