feat(mcp-client): auto-reconnect with bounded backoff after transport close

A per-instance connection supervisor restarts the original server config
with exponential backoff when the transport closes, re-runs tool discovery
on success, and atomically replaces the previous generation. Default policy
retries for ~2.5 minutes (10 attempts, 500ms→30s doubling) before giving up
and unregistering the server's tools.

New config block reconnect { enabled, initialDelayMs, maxDelayMs, maxAttempts }
on both transports; misconfiguration fails plugin load. A connection that
survives past the stability window (maxDelayMs) resets the attempt budget,
so occasional crashes recover indefinitely while a crash loop still exhausts
the cap.

Integrates with the upstream failOnStartupError: the initial sync uses
registrationFailure:'throw' when that flag is set so a squatted namespace
still rejects activation.

Fixes #1746

pnpm-lock.yaml

@@ -4901,6 +4901,9 @@ importers:
       '@deepseek-ai/dsh-subprocess':
         specifier: workspace:^
         version: link:../../subprocess/subprocess
+      '@deepseek-ai/dsh-timeout':
+        specifier: workspace:^
+        version: link:../../util/timeout
       '@deepseek-ai/dsh-tools':
         specifier: workspace:^
         version: link:../../core/tools