fix(Network): guard reserved request IDs against prototype pollution

[dvd233]

Summary

Fixes #734 by hardening VConsoleNetworkModel.updateRequest() against reserved and
inherited request IDs.

• Reject __proto__, constructor, and prototype before any request data is merged.
• Use an own-property check when deciding whether an existing request can be updated,
  so inherited names such as toString are not treated as stored requests.
• Add a browser demo control that exercises both public network.update() and
  network.add() entry points and reports whether global prototypes remain unchanged.

Validation

• npm run build (web bundle)
• npm run build:wx (WeChat bundle)
• npm run build:typings
• npm pack --dry-run --json
• Browser regression probe: reserved IDs are ignored, inherited IDs remain usable, and
  no marker is added to Object.prototype or Object.
• git diff --check

No public API shape changes; ordinary request IDs and updates retain their existing
behavior.