Add Unix socket reconnect and Session daemon state restore

[bk203]

Summary

• Add opt-in ReconnectingTransport that reconnects on ConnectionException and invalidates stale socket fds
• Add ReconnectableTransportInterface so Session replays daemon-side EVENT_REGISTER after reconnect via restoreDaemonState()
• Retry request() / requireSuccess() once on connection loss; harden streamedRequest() cleanup on disconnect
• Add ConnectionFailureContext on ConnectionException with getDetailedMessage() for transport diagnostics (stream metadata, endpoint, partial I/O, PHP errors)

Test plan

• composer test (67 tests)
• composer stan (PHPStan level 8)
• Unit tests for transport reconnect, invalidation, and wrapper retry
• Integration tests for server restart, event replay, mid-command retry, and streamed request fail-fast
• Unit tests for ConnectionException diagnostics and enriched failure context

[bk203]

Update: Added commit 88f8fb1 — ConnectionException now carries a ConnectionFailureContext with stream metadata, endpoint state (including whether the Unix socket file exists), partial read/write progress, and PHP error text. Use $e->getDetailedMessage() in catch blocks to diagnose stale-socket failures without restarting the app.