Implements Task 9 from docs/superpowers/plans/2026-06-13-decomp-only-followups.md
— the pre-purchase commit endpoint the client fires from StarterClassSelectDialog
before opening a RotationStarterCardPack. Without this the per-class draw path
from yesterday's work is unreachable: the dialog blocks on the AJAX call and
never advances to /pack/open.
Wire surface:
- POST /pack/set_rotation_starter_class { pack_id, class_id } → EmptyData.
Validates 1..8, rejects unknown packs (404), non-RS packs (400), and second
commits (400 — one-shot per pack per spec).
- PackConfigDto carries selected_class_id (nullable, omitted via global
WhenWritingNull policy when unset). Placement verified against decomp at
PackInfoTask.cs:86 — it's on the parent PackConfig, NOT the child gacha as
the original plan text had it.
- /pack/open cross-checks request.class_id against the persisted choice for
RS packs; rejects 400 on missing-commit or class-mismatch so a tampered
request can't swap pools after the choice is locked.
Storage:
- ViewerPackStarterClass owned entity; (ViewerId, PackId) unique index via the
pattern from project_owned_collection_unique_index memory.
- Migration PackStarterClass — composite PK + FK cascade verified against
fresh Postgres bootstrap.
Tests (9 new in PackControllerSetRotationStarterClassTests):
- Round-trip set → /pack/info shows selected_class_id.
- Field absent before any commit.
- Invalid class (0/9/-1/100) → 400.
- Already-chosen rejection.
- Non-RS pack / unknown pack rejection.
- /pack/open rejects no-prior-commit AND class-mismatch; succeeds when class
matches the persisted choice.
Full suite: 1552 passed (1543 + 9).
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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