feat(wallets): reuse WalletConnect sessions and pairings

[towanTG]

Summary

• reuse compatible WalletConnect sessions instead of disconnecting the existing one on every connect
• reuse an existing pairing when requesting a broader chain set so users can add chains without forcing a full reset
• request broader chain coverage as optional namespaces for the selected namespaces
• keep the active wallet object in sync with session update/delete/expire events
• add a patch changeset for @swapkit/wallets

Problem

The current connector always disconnects the first existing WalletConnect session before connecting again. That breaks normal session restoration and makes chain expansion unnecessarily destructive.

What changed

• if an existing session already satisfies the requested chains, reuse it directly
• if not, prefer an existing pairing topic and create a new proposal on that pairing
• stop force-resetting prior sessions during connect
• keep accounts and session updated from WalletConnect session lifecycle events
• harden the EVM signer against a missing session reference

Notes

This keeps the external WalletOption.WALLETCONNECT API intact.
It does not migrate the modal UI to Reown AppKit yet; this PR is scoped to session reuse and add-chain behavior.

Verification

• bun run --filter @swapkit/wallets build
• direct tsc output filtered to walletconnect/index.ts and walletconnect/evmSigner.ts came back clean
• full repo tsc in this worktree still has broader workspace-resolution noise unrelated to this change