perf: make remote-comms timing constants configurable, optimize e2e tests

Add reconnectionBaseDelayMs, reconnectionMaxDelayMs, handshakeTimeoutMs,
writeTimeoutMs, and ackTimeoutMs to RemoteCommsOptions so that e2e tests
can use fast values instead of the production defaults (500ms-10s backoff,
10s ACK/handshake/write timeouts).

Thread the new options through the full stack: RemoteCommsOptions → RPC spec
→ transport → ReconnectionManager/HandshakeDeps/RemoteHandle, and update the
browser runtime comms-query-string serializer.

Restructure the e2e test lifecycle: move the relay server to beforeAll/afterAll,
remove unnecessary delay() calls, reduce waitUntilQuiescent intervals, and
set fileParallelism: false in the e2e vitest config to prevent port conflicts
between relay-dependent test files.

Reduces remote-comms e2e suite from ~215s to ~97s (55% reduction).

Closes #904

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: sirtimid

packages/kernel-browser-runtime/src/utils/comms-query-string.ts

@@ -52,6 +52,11 @@ const NUMBER_PARAM_NAMES = [
   'stalePeerTimeoutMs',
   'maxMessagesPerSecond',
   'maxConnectionAttemptsPerMinute',
+  'reconnectionBaseDelayMs',
+  'reconnectionMaxDelayMs',
+  'handshakeTimeoutMs',
+  'writeTimeoutMs',
+  'ackTimeoutMs',
 ] as const satisfies readonly NumberParamKey[];
 
 const NonNegativeInteger = min(integer(), 0);