Inject automation: inject-message automation and runtime endpoint #437

Description

(prototype done; remaining work is review, polish and the release)

Add the editor automation automation/inject-message ({ id, msg? }) and the runtime route POST /nr-assistant/inject. Together they inject a message into a deployed node.

• Editor checks: refuse unknown nodes, nodes with no input port, disabled nodes or tabs, nodes inside a subflow definition, and nodes with undeployed changes. Return success: false with a reason.
• Runtime:
  • Requires write permission.
  • Re-checks AI Flow Deploy on every call through the shared getAutoDeployPolicy(), which fails closed.
  • Looks up the node with RED.nodes.getNode, replaces _msgid, calls node.receive(), and returns { injected, msgid }.
• Refusal code: INJECT_NOT_ALLOWED when the policy is off.
• Audit: RED.log.audit({ event: 'nr-assistant.inject', node, type, name, z }, req). Add name and z to the current prototype so forge can show details.
• Tests: unit tests for the editor action and the route.

Acceptance criteria:

• Injecting into a deployed function node shows up in the downstream debug with the returned msgid.
• With AI Flow Deploy off, the route returns injected: false, code: INJECT_NOT_ALLOWED, and nothing is delivered.

Epic/Story

No response