fix(bitswap): skip identify race when peer protocols are already known

[Rinse12]

Problem

Network#connectTo awaits Promise.all([libp2p.dial, raceEvent('peer:identify', filter for BITSWAP_120)]). peer:identify is single-shot per peer per process. If the peer was already identified before bitswap calls connectTo (common when the host app dials peers via other subsystems — pubsub, fetch, kad-dht, manual dial), the raceEvent waits for an event that will never re-fire and connectTo hangs indefinitely.

This blocks findAndConnect's find-providers fallback, so wantBlock is forced to time out instead of resolving from already-connected bitswap-speaking peers.

Fix

Before the race, check libp2p.peerStore.get(peer). If the peer is already known and advertises BITSWAP_120, return from a plain dial() (cheap no-op when already connected). Otherwise fall through to the existing identify-race code path unchanged. Guarded with isPeerId(peer) so the existing PeerId | Multiaddr | Multiaddr[] signature still works.

Safety

• connectTo callers (findAndConnect at network.ts:319 and 330) discard the returned Connection and use connectTo only for its peer-warmup side effect.
• The actual bitswap stream is opened later in sendMessage via libp2p.dialProtocol(peerId, BITSWAP_120), which performs its own protocol negotiation. So a fast-path-returned connection whose bitswap stream is in fact broken is detected and retried by sendMessage — no invariant is violated.

Measured effect

In an IPNS-over-pubsub workload where pubsub-mesh warmup dials the same peers that bitswap later wants providers from, median `wantBlock` wall time drops ~17% (3823 → 3192 ms over n=230 fetches). The improvement matches the theoretical save: the identify-race wait on already-identified peers is eliminated.

Tests

Added two tests in `packages/bitswap/test/network.spec.ts`:

• "should not wait for peer:identify when the peer is already known to speak bitswap" — stubs `peerStore.get` to return a peer whose `protocols` already contain `BITSWAP_120`, calls `connectTo`, and asserts the call resolves without subscribing to `peer:identify`. Pre-patch this test would hang because no `peer:identify` event is dispatched.
• "should fall through to the identify race when the peer is not yet in peerStore" — stubs `peerStore.get` to reject, simulates `peer:identify` firing after `dial`, and asserts the slow-path subscription is still installed. Guards against the fast-path swallowing the unknown-peer case.

Lint, dep-check, and the full bitswap node test suite (66 tests) all pass.