Refactor peer connection state machine into separate files

Split the monolithic peer.ts file into a modular state-based architecture:
- Created separate files for each state class (idle, creating-offer, waiting-for-answer, answering, exchanging-ice, connected, failed, closed)
- Extracted shared types into types.ts
- Extracted base PeerState class into state.ts
- Updated peer/index.ts to import state classes instead of defining them inline
- Made close() method async to support dynamic imports and avoid circular dependencies
- Used dynamic imports in state transitions to prevent circular dependency issues

This improves code organization, maintainability, and makes each state's logic easier to understand and test.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/peer/exchanging-ice-state.ts

@@ -0,0 +1,74 @@
+import { PeerState } from './state.js';
+import type { PeerOptions } from './types.js';
+import type RondevuPeer from './index.js';
+
+/**
+ * Exchanging ICE candidates and waiting for connection
+ */
+export class ExchangingIceState extends PeerState {
+  private pollingInterval?: ReturnType<typeof setInterval>;
+  private timeout?: ReturnType<typeof setTimeout>;
+  private lastIceTimestamp = 0;
+
+  constructor(
+    peer: RondevuPeer,
+    private offerId: string,
+    private options: PeerOptions
+  ) {
+    super(peer);
+    this.startPolling();
+  }
+
+  get name() { return 'exchanging-ice'; }
+
+  private startPolling(): void {
+    const connectionTimeout = this.options.timeouts?.iceConnection || 30000;
+
+    this.timeout = setTimeout(async () => {
+      this.cleanup();
+      const { FailedState } = await import('./failed-state.js');
+      this.peer.setState(new FailedState(
+        this.peer,
+        new Error('ICE connection timeout')
+      ));
+    }, connectionTimeout);
+
+    this.pollingInterval = setInterval(async () => {
+      try {
+        const candidates = await this.peer.offersApi.getIceCandidates(
+          this.offerId,
+          this.lastIceTimestamp
+        );
+
+        for (const cand of candidates) {
+          if (cand.candidate && cand.candidate.candidate && cand.candidate.candidate !== '') {
+            try {
+              await this.peer.pc.addIceCandidate(new RTCIceCandidate(cand.candidate));
+              this.lastIceTimestamp = cand.createdAt;
+            } catch (err) {
+              console.warn('Failed to add ICE candidate:', err);
+              this.lastIceTimestamp = cand.createdAt;
+            }
+          } else {
+            this.lastIceTimestamp = cand.createdAt;
+          }
+        }
+      } catch (err) {
+        console.error('Error polling for ICE candidates:', err);
+        if (err instanceof Error && err.message.includes('not found')) {
+          this.cleanup();
+          const { FailedState } = await import('./failed-state.js');
+          this.peer.setState(new FailedState(
+            this.peer,
+            new Error('Offer expired or not found')
+          ));
+        }
+      }
+    }, 1000);
+  }
+
+  cleanup(): void {
+    if (this.pollingInterval) clearInterval(this.pollingInterval);
+    if (this.timeout) clearTimeout(this.timeout);
+  }
+}