fix(extension): harden websocket reconnect lifecycle

[BB-fat]

Supersedes #19 — rebased onto current main and conflicts resolved. All credit to @NianJiuZst.

Conflict resolution notes

Rebased onto main after #17 landed; the two redundant commits (Biome formatting, port test fix) were dropped automatically since their content already reached main via #17. The remaining conflict in apps/extension/src/lib/connection-controller.ts was resolved by composing both changes instead of picking a side:

• Kept fix(runtime): clean up sessions on disconnect #17's ConnectionLifecycleHooks (beforeDisconnect / onDisconnected) and the serialized recoverFromDisconnect() path (explicit disconnect to cancel WSTransport's internal reconnect timer before session teardown, then reconnect).
• Layered fix(extension): harden websocket reconnect lifecycle #19's handshake race hardening on top: per-handshake generation counter + AbortController (this supersedes fix(runtime): clean up sessions on disconnect #17's handshakeInFlight boolean, which was removed rather than duplicated), AbortSignal plumbed into performHandshake, and the 1s handshake retry timer.
• Folded fix(extension): harden websocket reconnect lifecycle #19's "cancel in-flight handshake on disconnect" into fix(runtime): clean up sessions on disconnect #17's disconnected branch, so a late handshake resolution can never clobber the next connection.
• runHandshake's deliberate disconnects (rejected peer, failed-handshake bounce) now set a flag so they skip unexpected-loss recovery — the retry timer owns that reconnect. This also avoids a reconnect loop where a version-rejected peer would be re-dialed immediately by fix(runtime): clean up sessions on disconnect #17's recovery.
• recoverFromDisconnect() bails out if another path already reconnected while it yielded (state no longer disconnected).

Verification

• pnpm lint (biome check + stylelint): clean
• tsc --noEmit: clean
• vitest run: 571 passed / 48 failed — all 48 are the pre-existing React.act is not a function failures in .tsx popup/overlay tests; identical failure set on origin/main (48 there as well), so no regression. The 4 new tests from this PR pass.