docs: mark SP3 shipped; tick all plan checkboxes

README.md

@@ -123,16 +123,45 @@ backup API).
 
 ## Roadmap
 
-Sub-project 2 (DB + reconciliation) is **shipped**. The other two:
+Sub-projects 2 and 3 are **shipped**. Next up:
 
-- **Sub-project 3 — More 837P/835 features.** Additional 837P validation
-  rules (REF*G1 enforcement, BHT06), 835 CAS deep-parsing, 999 ACK, and
-  270/271 eligibility.
+- **Sub-project 3 (shipped) — More 837P/835 features.**
+  - **837P validation rules:** R034 enforces `REF*G1` on frequency-code
+    7/8 claims; R035 enforces `BHT06` transaction-type-code is in the
+    allowed set per payer config.
+  - **835 CAS deep-parsing:** every CAS adjustment now surfaces with its
+    CARC reason code + label (e.g. `CO-29: The time limit for filing has
+    expired`), surfaced via `GET /api/remittances/{id}` and rendered as
+    an expansion row on the Remittances page.
+  - **999 ACK transaction set:** full inbound parser + outbound
+    serializer. Auto-generated on 837 ingest when `?ack=true` is passed
+    to `POST /api/parse-837`. Persisted to the `acks` table, browsable
+    on a new `/acks` page, and downloadable as the regenerated raw
+    999 text.
+  - **270/271 eligibility (API-only):** `POST /api/eligibility/request`
+    builds a 270 from a JSON payload (subscriber, provider, payer,
+    service type); `POST /api/eligibility/parse-271` ingests the
+    response and returns structured `coverage_benefits`.
 - **Sub-project 4 — Frontend features.** Per-claim detail drawer, batch
   diff view, real-time streaming of NDJSON GET responses, advanced
   filters (date range, multi-status, saved filter sets), keyboard-driven
   navigation.
 
+### SP3 endpoints
+
+- `POST /api/parse-837?ack=true` — existing 837 parse, plus optional
+  auto-generated 999 ACK persisted alongside the batch.
+- `POST /api/parse-999` — parse an inbound 999 ACK and persist it.
+- `GET /api/acks` — list ACKs.
+- `GET /api/acks/{id}` — ACK detail, including the regenerated
+  `raw_999_text`.
+- `POST /api/eligibility/request` — build a 270 from JSON.
+- `POST /api/eligibility/parse-271` — ingest a 271 and return parsed
+  coverage benefits.
+
+The UI gains a new **Acks** page (sidebar entry) that lists persisted
+ACKs and lets you download the regenerated 999 text.
+
 ## License
 
 No license file yet; this is internal-use software. Add a `LICENSE` file