chore(spec): regenerate the flow reference after merging main

Net delta vs origin/main is exactly the two input-shape lines #4415 intends
(`inputSchema[].required`, `boundaryConfig.interrupting` render optional now
that FlowNode is read from the pipe's authorable IN side).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BickTBKm2JYSNnrtPT8ysa

Author: claude

content/docs/references/automation/flow.mdx

@@ -8,19 +8,13 @@ description: Flow protocol schemas
 Flow Node Types — **built-in seed set** (ADR-0018).
 
 Historically this `z.enum` *gated* `FlowNodeSchema.type`, which made the
-
 closed protocol reject any plugin-registered node type — defeating the open
-
 runtime registry (`registerNodeExecutor(type: string)`). Per ADR-0018 the
-
 gate is removed: `FlowNodeSchema.type` is now a validated `string`, checked
-
 against the live action registry at `registerFlow()` time, not frozen here.
 
 `FlowNodeAction` is **retained** as the canonical list of built-in type ids
-
 (documentation + the seed descriptor set the engine registers at boot). It
-
 no longer constrains authored flows — plugins extend the vocabulary.
 
 <Callout type="info">