CS08A — Helpfulness client layers

Date: 2026-10-11. Status: LOCAL_DONE. Scope: domain ports, use case, flag store, HTTP client + unit tests — no DI, no ViewModel, no panel (CS08B), no VPS/APK. Head: maintained dev. Plan: phased plan. Rules: B-BR-CS01, BUC-CS02.

Added (mirrors the vote stack, frozen wire from CS02B)

• CommunityHelpfulnessPorts.kt: HELPFUL/NOT_HELPFUL frozen set, reject kinds (SELF_VOTE, STALE_REVISION, INELIGIBLE_TARGET, QUOTA_EXCEEDED, INVALID_VOTE, CONFLICT, TRANSPORT), exact receipt/tally shapes (basis points and choice nullable), CommunityHelpfulnessGateway.
• SubmitHelpfulnessVoteUseCase: flag gate (Disabled, no IO), blank/choice/sequence validation throwing DomainException, cast/change/remove/tally with fixed-kind sanitized rejections.
• CommunityHelpfulnessFlagStore: default OFF SharedPreferences.
• CommunityHelpfulnessHttpClient: cast/remove/tally routes with stable submission ids, Idempotency-Key, exact parsing (percentage and choice absent on zero/anonymous), backend-code → kind mapping, fixed error text only.

Validation (actual)

• Application: 6/6 green (disabled silence, exact tally, blank/ choice/sequence refusal, self/stale kinds, transport honesty, remove/tally).
• Data (MockWebServer): 4/4 green (tally parse + overlay, empty tally omits percentage, 7 backend codes, remove posts sequence only). Full :application:test green.
• git diff --check clean; CI Android runs ./gradlew test (no lint gate configured).

Limits / owed (CS08B)

• DI bindings, ViewModel + card/panel, guest-login explanation, Denunciar reuse of the dispute flow, TalkBack/large-text checks, device matrix (CS14-owned).

Next microtask: CS08B — ViewModel, panel, DI, guest.