MetaMask (Tezos snap) wallet connect hangs during Beacon pairing

## Symptom

Connecting a wallet via **MetaMask** on Tezos networks opens the Beacon pairing deeplink to `metamask.tezos.com/?type=tzip10&data=…`, and the flow hangs there — the handshake back to the dapp never completes. The block-explorer link shown by the bridge page reports "account not valid".

Kukai and Temple connect fine over the same Beacon pairing (observed 2026-08-13 on production).

## What has been ruled out

- **Not a regression from the 2026-08 dependency merges** (#957, #946): no beacon-, taquito-, or walletconnect-transport packages changed in the lockfile across those merges. The MetaMask entry in the pairing UI comes from `@ecadlabs/beacon-ui` (via `@taquito/beacon-wallet` v24), unchanged since the Taquito v24 upgrade (#947, March 2026).
- **Bridge/snap not obviously dead upstream**: metamask.tezos.com serves 200; [airgap-it/tezos-metamask-snap](https://github.com/airgap-it/tezos-metamask-snap) had commits through Jan 2026 and has no open issues reporting this.

## Suspected causes (unconfirmed)

1. Long-standing breakage in the Beacon P2P handshake between the bridge page / snap and the dapp, unnoticed due to low usage of the MetaMask path.
2. Stale local snap state (MetaMask → Snaps → remove "Tezos Wallet" → reconnect reinstalls it) — not yet ruled out.

## Next steps when picked up

- Reproduce with browser console open on both the dapp and the bridge tab; capture where the pairing stalls (matrix transport vs. snap RPC).
- Test against a pre-2026-08 build to fully rule out regression.
- If broken upstream: file against the snap repo and consider hiding MetaMask from the Beacon wallet list until fixed, so users don't hit a dead-end connect flow.

Reproduce the MetaMask Tezos snap pairing with browser consoles open on both the dapp and bridge tab. Trace whether the stall occurs in the matrix transport or snap RPC, then compare with a pre-2026-08 build. Done means identifying the failure source and, if it is upstream, filing it against the snap repository and assessing whether MetaMask should be hidden from the Beacon wallet list.

Written by the indexing model from the issue text.