Session-destroying paths:
- reconnectSession() no longer routes an extension reconnect failure into
  its WalletConnect catch-all, which called disconnect() and so revoked
  the origin in the wallet. A transient -32603/-32004, or a wallet on
  another network, now rejects with the transport's own error (cause at
  error.data.type rather than buried under a second wrapper) and leaves
  the approval and the stored details intact.
- A successful extension connect retires the WalletConnect pairing left
  in flight, so a QR scan that lands afterwards can no longer overwrite
  the extension session with a mobile one.
- The connect modal comes down before the provider is awaited, so its
  close button can no longer reject a connect whose later approval still
  stores the session behind the dApp's back.

Event surface:
- The WalletConnect disconnect path now clears storage and nulls the
  connector before the handler runs, matching what the README documents
  and what the extension path already did.
- Our own killSession() (in connect() and disconnect()) no longer reaches
  the dApp as a wallet-side disconnect.
- networkChanged is gated on an extension-owned session, so a dApp on a
  mobile session is not told to repoint its algod client because the
  installed extension switched network.
- dispose() is public: an instance otherwise stays subscribed to
  window.pera for the page's life, and under StrictMode/HMR the discarded
  instance swallows the events the live one should handle.

Also: signData filters non-string entries before decoding (atob(null)
decoded "null" into three plausible-looking signature bytes) and rejects
a non-array response as SIGN_DATA; isPeraProviderError duck-types instead
of relying on instanceof across realms; and the web-wallet-unavailable
stylesheet only force-expands the accordion when a single option is left,
rather than opening both the extension and QR rows uncollapsibly.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>