fix(memos-local-plugin): harden hermes bridge lifecycle

[liuhaibin0528]

Summary

This hardens the Hermes stdio bridge lifecycle for apps/memos-local-plugin.

• terminate orphaned non-daemon bridge.cts --agent=hermes processes on client close
• recreate the bridge if the cached Python client points to a dead child process
• isolate feedback.submit failures so they do not abort sync_turn
• use a longer timeout for turn.end and a shorter timeout for feedback.submit
• add Python regression coverage for the new bridge lifecycle behaviors

Why

In long-running Hermes sessions I hit two stability problems repeatedly:

1. stale stdio bridge children accumulated after reconnects/timeouts
2. a slow or failed feedback.submit could make the whole turn sync look failed even though turn.end had already completed

This patch keeps the viewer daemon behavior intact while making the short-lived stdio bridge process lifecycle explicit.

Testing

• python3 -m unittest apps.memos-local-plugin.tests.python.test_bridge_client
• python3 -m unittest apps.memos-local-plugin.tests.python.test_hermes_provider_pipeline