A person puts a ready issue first: MCP `map` `first` and the map page reorder what the crew starts next #7657

Part of #7640. Say "this first" without assigning issues one at a time.

Done when:

• [ ] MCP map takes { repo, first: <number> } (writers) and the map page has a First button on a ready issue; the dispatcher starts ranked ready issues before the rest
• [ ] The rank is an event with the actor; a closed or blocked issue cannot be put first (invalid)
• [ ] A test ranks issue B over A and finds the dispatcher picks B

Files: src/http/mcp/tools/map.ts, src/crew/dispatch.ts, src/web/pages/map.ts, test/map-first.test.ts

Risks: Keep pillars' order: a rank reorders within what is ready, it never lifts the Later gate.

Fits: a builder

Parked by the crew: the check failed ("ranking B over A puts B first and the dispatcher picks it") and the decider saw no point in another try try 1: README.md, docs/MCP.md, src/actions/first.ts, src/core/dependencies.ts (+10 more) (pull #7739 closed). Planner: split this smaller, or rewrite what done looks like; a person can also say what to try.

Parked by the crew: the check failed ("event audience coverage > every kind the source emits is classified") and the decider saw no point in another try try 1: docs/MCP.md, docs/design/areas/map.md, docs/features/map-first.md, src/actions/first.ts (+13 more) (pull #7773 closed).

Parked twice since a person last spoke here, so it is the planner's now. Every reason:

1. the check failed ("ranking B over A puts B first and the dispatcher picks it") and the decider saw no point in another try try 1: README.md, docs/MCP.md, src/actions/first.ts, src/core/dependencies.ts (+10 more) (pull #7739 closed)
2. the check failed ("event audience coverage > every kind the source emits is classified") and the decider saw no point in another try try 1: docs/MCP.md, docs/design/areas/map.md, docs/features/map-first.md, src/actions/first.ts (+13 more) (pull #7773 closed)

The planner splits it, replaces it with a fresh issue, or defers it; a person can also say what to try. Nothing starts here until then, and the board lists it.

Split by the planner into #7806 (the rank in the core, with its event classified in event_audience.ts, which sank #7773, and the dispatcher test), #7807 (MCP map first) and #7808 (the map page First button). Both tries touched 14 to 17 files in one pull. Each slice now names three to five.