v2.18.2 — reframe update step 2 as enumerate-and-copy (ADR-0042)

Bugfix release — a second patch on the copy-driven update thread.

v2.18.1 fixed the immediate miss by wording step 2's list as non-exhaustive, but step 2 was still a prose paragraph an agent interprets file-by-file — under-copying became wrong, not impossible. This patch removes the interpretation at the source.

Changed

• ADR-0042 (idea 0036 → plan 0031; amends ADR-0022) — updating.agent.md step 2 is reframed as a deterministic enumerate-and-copy rule: "copy every subfolder you detect under the source''s starter/docs/, with all contents, overwriting — except the project-authored preserve-list." Because the agent discovers subfolders instead of reading a named example list, a future scaffold subtree (like v2.18''s docs/scripts/) is picked up automatically and can''t be silently dropped — and no per-folder instruction line is ever needed. starter/ stays the single source of truth; no manifest; ADR-0022''s mechanics unchanged (execution-detail amendment only).

Adopter migration

None. Pure wording refinement — enumerate-and-copy lands exactly the same files; it only makes a future under-copy impossible to author. A fresh update naturally uses the sharper wording.