Correct MVP-cut registry verification in decomposition scaffolding plan

[Copilot]

Task 8 in the decomposition scaffolding plan used a grep check that matched every "MVP cut" occurrence in docs/decomposition.md, even though the document intentionally contains that phrase in multiple places. This updates the check to validate the unique registry separator row instead of the ambiguous phrase.

• Plan verification

  • Replaced the Task 8 Step 4 command in docs/superpowers/plans/2026-04-16-spec-decomposition-scaffolding.md
  • The check now targets the exact dashed table row that marks the cut line, so the expected count of 1 is actionable

  grep -c -- "--------- MVP cut ---------" docs/decomposition.md

• Referenced registry content

  • Added the corresponding docs/decomposition.md registry content used by the plan so the verification target is present on this branch

• Consistency cleanup

  • Aligned copied documentation details that conflicted with the scaffolding rules:
    • f-identity-and-auth starts at stub
    • f-public-api depends on f-identity-and-auth using the canonical ID