refactor(mcp): consolidate documentation into mcp.schema.ts

Single file to update when the data model changes:
- EVENT_TIMER_FIELDS and EVENT_WRITABLE_FIELDS (tool JSON schemas) moved from mcp.tools.ts
- ONTIME_SCHEMA_MARKDOWN and ONTIME_DOCS_MARKDOWN moved from mcp.resources.ts
- mcp.tools.ts and mcp.resources.ts now import from mcp.schema.ts
- Removed inline data model notes from the agenda prompt; replaced with a reference
  to the ontime://schema resource
- Fixed inaccurate enum values in schema (Milestone type added, TimerType/EndAction
  corrected to match ontime-types)

https://claude.ai/code/session_01U24MeuUacYXeQhbX3tatEe

apps/server/src/api-mcp/mcp.prompts.ts

@@ -46,12 +46,7 @@ export function handleGetPrompt(name: string, args: Record<string, string>): Get
           content: {
             type: 'text',
             text: `Convert the following agenda into an Ontime rundown.
-
-Data model:
-- Times are milliseconds from midnight. 09:00 = 32400000, 10:30 = 37800000, etc.
-- duration = timeEnd - timeStart
-- endAction: "load-next" for back-to-back sessions, "none" otherwise
-- Ask the user what cue naming and colour conventions they prefer
+Read the ontime://schema resource if you need a data model reference.
 
 Steps:
 1. Call ontime_get_rundown to see current state and identify an \`after\` anchor if appending.