Define the Web scope passport and native exclusion boundaries

Changes: Add proposed scope ADR with reasons for all ten excluded IDs, retained Web obligations, lifecycle limits, external provider roles and deferred decisions. Add a document coverage/lifecycle checker with four negative mutations and executor evidence/handoff for security review.
Validation: python3 experiments/0000-scope/check.py passed for ten excluded IDs and seven lifecycle scenarios; all four negative mutations were rejected. make check passed validation and 66 tooling tests. Whitespace and allowed source paths checked. No live browser or provider integration was tested; ADR awaits independent review.
