docs+plans: reconcile blueprint with ambition, add ADRs, sequence workplans

Aligns the v1 architecture with the longer-horizon platform thesis so we can
start implementation without the schema-level inconsistencies the prior
review surfaced.

ADRs (docs/adr/0001..0006): content-addressed dual-digest storage, append-only
event log as source of truth, canonical CBOR manifests, control/data-plane
contract, v1 tech stack (Python 3.12 / uv / FastAPI / SQLAlchemy Core +
asyncpg / Alembic / cbor2 / blake3 / ruff / mypy / pytest / typer), OCI
compatibility kept reachable.

Architecture blueprint rewritten to v2: library-first (ffmpeg-shaped) module
layout, materialised-view data model over the event log, upload-session and
event-stream endpoints pinned, retrieval tiering promoted into the schema.

Roadmap added (docs/ROADMAP.md) with three phases. WP-0001 rewritten as the
Foundation plan (scaffold + kernels + local FS + minimal app). WP-0002..0005
created carrying the existing state_hub_task_ids forward semantically:
ingestion API (T004), retention lifecycle (T005), S3-compatible backend
(T006), guide-board pilot (T007). T001/T002/T003/T008 remain in WP-0001
with refined acceptance.

README and AGENTS.md refreshed to reflect the new repo shape.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

README.md

@@ -1,17 +1,51 @@
 # artifact-store
 
-Generic artifact registry and storage gateway for generated outputs, evidence
-packages, reports, logs, and release artifacts.
+Generic artifact registry and storage gateway for generated outputs,
+evidence packages, reports, logs, snapshots, exports, and release
+artifacts.
 
-The registry owns artifact identity, metadata, provenance, retention policy, and
-retrieval records. Actual bytes are delegated to configured storage backends such
-as a local filesystem, S3-compatible object storage, or Ceph RGW.
+The registry owns artifact identity, metadata, provenance, retention
+policy, and retrieval records. Bytes are delegated to configured
+storage backends (local filesystem in v1, S3-compatible / Ceph RGW
+next).
 
-Start here:
+The shape is library-first (`artifactstore` Python package); the HTTP
+server and the CLI are thin consumers. Content is addressed by digest;
+state is authoritative in an append-only event log; materialised views
+are rebuildable.
 
-- [INTENT.md](INTENT.md) — purpose, product thesis, scope, boundary
-- [docs/ARCHITECTURE-BLUEPRINT.md](docs/ARCHITECTURE-BLUEPRINT.md) — draft architecture
-- [docs/PLATFORM-AMBITION.md](docs/PLATFORM-AMBITION.md) — longer-horizon thesis and the schema commitments v1 preserves
-- [docs/REVIEW-2026-05-15-intent-and-blueprint.md](docs/REVIEW-2026-05-15-intent-and-blueprint.md) — SWOT and optimisation review
-- [docs/ASSEMBLY-EXPERIMENT.md](docs/ASSEMBLY-EXPERIMENT.md) — opt-in research line on hand-tuned assembly for hot kernels
-- [workplans/ARTIFACT-STORE-WP-0001-service-baseline.md](workplans/ARTIFACT-STORE-WP-0001-service-baseline.md) — first implementation workplan
+## Status
+
+Concept / service-baseline planning. No runnable scaffold yet —
+`workplans/ARTIFACT-STORE-WP-0001-service-baseline.md` is the next step.
+
+## Start here
+
+- [INTENT.md](INTENT.md) — purpose, product thesis, scope, boundary.
+- [SCOPE.md](SCOPE.md) — lightweight orientation.
+- [docs/ARCHITECTURE-BLUEPRINT.md](docs/ARCHITECTURE-BLUEPRINT.md) — the
+  v2 architecture: modules, data model, API shape.
+- [docs/PLATFORM-AMBITION.md](docs/PLATFORM-AMBITION.md) — longer-horizon
+  thesis, ffmpeg / VLC reference points, the schema commitments v1
+  preserves.
+- [docs/ROADMAP.md](docs/ROADMAP.md) — workplan sequencing across
+  phases.
+- [docs/adr/](docs/adr/) — architecture decision records (ADR-0001 …
+  ADR-0006).
+- [docs/ASSEMBLY-EXPERIMENT.md](docs/ASSEMBLY-EXPERIMENT.md) — opt-in
+  research line on hand-tuned assembly for hot kernels.
+- [docs/REVIEW-2026-05-15-intent-and-blueprint.md](docs/REVIEW-2026-05-15-intent-and-blueprint.md)
+  — the SWOT review that triggered this cleanup.
+
+## Active workplans
+
+- [WP-0001 — Foundation: scaffold, core kernels, local FS backend](workplans/ARTIFACT-STORE-WP-0001-service-baseline.md)
+- [WP-0002 — Ingestion API and manifest surface](workplans/ARTIFACT-STORE-WP-0002-ingestion-api.md) (planned)
+- [WP-0003 — Retention lifecycle](workplans/ARTIFACT-STORE-WP-0003-retention-lifecycle.md) (planned)
+- [WP-0004 — S3-compatible backend](workplans/ARTIFACT-STORE-WP-0004-s3-compatible-backend.md) (planned)
+- [WP-0005 — Guide-board pilot ingestion](workplans/ARTIFACT-STORE-WP-0005-guide-board-pilot.md) (planned)
+
+## Agent operating notes
+
+See [AGENTS.md](AGENTS.md) for the StateHub-integrated session
+protocol, workplan conventions, and progress-logging contract.