Turns the five founding ADRs, accepted 2026-08-27, into an ordered set
of implementation work items under the vault-core epic: which item
discharges which decision, what each depends on, and what is
deliberately not in the graph.

The beads are filed in the tracker; this document is the map. Eleven
core items block the epic, four hang after it, and two are upstream
watch items that stay unstarted until the engine moves.

Brings the README current with the accepted surface. The status moves
from scaffold to designed-not-built, the five records are named and
linked, the split with encryptor_ecto is stated, and the stale MIT
line is corrected to Apache-2.0 to match mix.exs.

Refreshes the ADR index, whose status column still read proposed for
all five records after they were accepted. No record's status line,
decision text, or amendment is touched.

Refs: enc-2y3