feat(adt): surface build-gone health on playtest detail + fix ChangeADTBuild persistence

[anggorodewanto]

What

Surface a gone/undownloadable ADT build on the playtest detail page instead of only at ApproveApplicant time, and fix a pre-existing ChangeADTBuild persistence bug found while building this.

Investigation (confirmed live)

The reported approve 400 (errorCode=1003303402 / ErrBuildNotFound) is accurate. Probing live ADT (develop.blackbox.accelbyte.io): downloadUrls 404s "build not found" even though the build still appears in ListBuilds — so a list-membership check is insufficient; the faithful signal is the side-effecting IssueDownloadURL call.

Surfacing (persist-at-approve + on-demand check)

• migration 0009: playtest.adt_build_status (OK/UNAVAILABLE, CHECK-enforced) + adt_build_checked_at
• CheckADTBuild RPC: on-demand probe of IssueDownloadURL, persists health. Ignores the fallback URL (a fallback masks a dead build for approval but doesn't make the build healthy). ErrBuildNotFound→UNAVAILABLE, success→OK; transient ADT errors don't clobber last-known status.
• approve / RetryDM record the same health opportunistically via resolveADTDownloadURL, before any fallback masks it
• repo: SetADTBuildHealth writer (deliberately does NOT bump updated_at)
• admin Distribution tab: build-health Alert + "Check build" button
• pth adt build check + smoke dry-run probe; errors.md (4 rows) + cli.md + STATUS_M5 C14

Bundled bug fix — ChangeADTBuild silently dropped the build change

PgPlaytestStore.Update's SET whitelist omits adt_game_id/adt_build_id, so ChangeADTBuild accepted the change and no-oped at the DB — the in-UI recovery path was broken. Its happy-path test passed only because the fake store cloned the whole struct. Now routes through a dedicated UpdateADTBuild writer with a real-PgStore integration regression test.

Verification

• go test ./... green (repo integration ran migration 0009 + new writers)
• golangci-lint run 0 issues; buf lint + idempotent proto regen
• admin: 89 vitest + npm run build
• make smoke PASS (full boot + new adt build check probe)

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