docs(morph-doc): adapt node operation guide for centralized sequencer

[curryxbo]

Background

Morph is moving node operation onto the centralized sequencer architecture. The current morph-doc node-operation documentation still describes the previous topology and operational flow, so it needs to be updated to match how nodes are actually run and operated under the centralized sequencer.

Goal

Update morph-doc so that node operators have an accurate, end-to-end guide for running and operating a node in the centralized-sequencer setup.

Scope / Tasks

• Describe the centralized-sequencer node topology and the role each component plays (sequencer vs. follower/verifier nodes).
• Update node setup / startup instructions (config, flags, env) to reflect centralized-sequencer mode.
• Document how follower nodes sync from / verify against the centralized sequencer.
• Update operational guidance: monitoring, health checks, upgrade / restart procedure.
• Call out behavior changes vs. the previous topology and any migration steps for existing operators.
• Cross-link with the run-morph-node changes (see companion issue).

Acceptance Criteria

• A node operator can follow the doc to bring up and operate a node against the centralized sequencer without referring to source code.
• Doc is consistent with the actual run-morph-node configuration/behavior.

Related

• Companion issue: run-morph-node configuration for centralized sequencer.