P20-T04 — Discovery acceptance and legacy regression

Status: LOCAL_DONE on codex/phase-20-community-discovery. Issue: #79. Phase P20 exit candidate: G20 scope (real community current-price browsing and station detail against local backend, with source/freshness/condition/accessibility/offline truth) is demonstrated at contract + journey level; backend community projection stays UNKNOWN until P04 (no fake coverage).

Regression evidence (rerun, current head 9a40d32)

• ./gradlew :domain:test :application:test :app:testDebugUnitTest :app:assembleDebug --no-daemon --rerun-tasks → BUILD SUCCESSFUL.
• :domain:test 397/0-fail · :application:test 238/0-fail · :app:testDebugUnitTest 128/0-fail (763 total, 0 failures/errors/skips).
• Targeted acceptance classes, all green: DiscoveryQueryTest 6, DiscoveryStationsRuleTest 7, StationDetailRuleTest 6, StationsViewModelTest 9 (search/cache/detail), CommunityPriceDisplayTest 7 (conditional prices: STANDARD needs no qualifier, APP/LOYALTY without qualifier stay pending, OTHER excluded from ranking), CommunityPricesViewModelTest 4, HomeViewModelTest 4.
• Accessibility: ColorContrastTest 2, FuelProductTintContrastTest 2, SourceTimeBadgeTest 3 (text + icon + screen-reader labels per source kind).
• Legacy/expert tools preserved: RoutesTest 6 + NavigationTabTest 6 green; nav graph still wires onboarding, home, community, profile, search, location, prices, history, stations (+fuel arg), vehicles, week picker, capture, auth deep link, settings — none removed by P20.
• git diff --check clean; scoped secret review (no secrets/PII/GPS/photo content).

Source/recency/price identification (contract level)

• Primary price is never an ANP substitution (BackendPriceGroup.create rejects non-null community; P20 detail shows explicit no-coverage + dated ANP reference with stale/unknown states).
• Guest explores without account/GPS; offline keeps cached lists with explicit banners; failed refresh preserves cache with retry.

Honest limits (not waived)

• No novice comprehension campaign ran here: P19-T02 recorded it pending and P24-T02 owns the usability/accessibility study with real participants.
• No device matrix, cold-start, heap/battery profiling: owned by P24-T03 on frozen devices.
• No map: deferred until provider/dependency/privacy audit (frozen IA).
• Community projection content (P04), photo journey (P21), social/moderation (P22): out of scope.
• Data module and backend suites untouched by P20 (no changes there); full production certification stays G09-deferred.