If Track-1 passes: ADR for intermediary-substrate pivot vs shut search

## Context
Only open after Track-1 PASS. Different company shape than end-laborer wedge.

## Acceptance
- [ ] ADR with options, consequences, reversal cost
- [ ] Does not invent TAM or metrics
- [ ] Updates pitch non-goals accordingly

## Refs
- ADR-0004 reversal signal
- C5 open question on whether intermediaries would buy a substrate