epic: Python SDK parity with JS @adcp/sdk@6.7 framework primitives

[bokelley]

Context

Building the v3 reference seller (PR #447) confirmed adopters hand-roll patterns that JS now ships as helpers. The JS 6.7 migration guide at docs/migration-6.6-to-6.7.md (in adcp-client-js) documents 15 recipes.

Goal

Ship the high-leverage 11 helpers as Python SDK primitives so adopters (Prebid salesagent, GAM-shaped publishers, etc.) get the same DX as JS.

Sequence

Batch 1 (parallel, no deps)

• feat(server): createUpstreamHttpClient + createTranslationMap (translator pattern helpers) #453 create_upstream_http_client + create_translation_map
• feat(server): composeMethod — typed before/after hooks with {shortCircuit: T} discriminated wrapper #454 compose_method + security composers
• feat(decisioning): state-machine helpers + typed exception classes + refAccountId #455 state-machine helpers + typed exceptions + ref_account_id
• feat(server): Account v3 wire fields + AccountStore.upsert/list/syncGovernance receive ResolveContext #456 Account v3 wire fields + AccountStore.upsert/list/sync_governance(ctx)

Batch 2 (depends on #456)

• feat(server): createTenantStore — opinionated multi-tenant AccountStore with fail-closed isolation #457 create_tenant_store
• feat(server): createOAuthPassthroughResolver — Shape B account resolver factory #458 create_oauth_passthrough_resolver
• feat(server): createRosterAccountStore — Shape C explicit AccountStore for publisher-curated rosters #459 create_roster_account_store

Batch 3 (DX polish)

• feat(validation): oneOf near-miss validator hints + issues[].hint on every VALIDATION_ERROR #460 oneOf near-miss validator hints
• feat(client): looksLikeV3Capabilities — drop the v2-downgrade footgun on capabilities-validation failure #461 looks_like_v3_capabilities client fallback heuristic
• feat(server): createMediaBuyStore — opt-in targeting_overlay echo for property-lists / collection-lists sellers #462 create_media_buy_store
• feat(decisioning): credential-leak guidance + write-only field strip on every echo path #463 credential-leak guidance + write-only strip on every echo path

Validation point

Refactor v3 reference seller to USE the new helpers (concrete demo).

Reference

JS changesets in adcp-client-js/.changeset/ (6.7 release).

[bokelley]

Triage

Classification: Feature request (epic — multi-batch, cross-cutting)
Bucket(s): handlers, client, validation (labels not present in repo — gap noted below)
Status: ready-for-human
Milestone: (omitted — no target version specified)

Assessment: Epic is well-structured. Batch 1 (4 parallel items) feeds Batch 2's dependency on AccountStore.upsert/list/sync_governance(ctx) from item #4; Batch 3 is independent DX polish. PR #447 (v3 reference seller motivating this) merged this morning. The Batch 1 item #4 (Account v3 wire fields + AccountStore) is the critical-path gate — Batch 2 cannot start until it lands.

My take: Keeping this as a tracking epic is correct. When child issues are filed, triage will process each one individually — Batch 1 items are non-breaking additions and Execute-eligible; Batch 2/3 items will be evaluated as each child lands. No auto-PR from this issue.

Label gap: handlers, client, and validation bucket labels do not exist in this repo. Adding them would enable label-based filtering across epic children.

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Triaged by Claude Code. Session: https://claude.ai/code/${CLAUDE_CODE_REMOTE_SESSION_ID}

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