docs(sp6): README — Inbox section

README.md

@@ -128,6 +128,46 @@ backoff schedule on error is `1s → 2s → 4s → 8s → 16s → 30s` capped.
 | ---------------------------- | ------- | ------------------------------------------------------- |
 | `CYCLONE_TAIL_HEARTBEAT_S`   | `15`    | Idle heartbeat interval (seconds). Lower it for tests.  |
 
+## Inbox
+
+`/inbox` is the working surface. Four lanes, dark by default (Ticker Tape
+aesthetic):
+
+- **Rejected** — claims whose 999 set-level response was R or E. Re-submit in bulk.
+- **Candidates** — remits whose CLP-claim-id didn't match exactly; each one shows its top scored claim. One-click manual match or dismiss.
+- **Unmatched** — claims still waiting for a remit, and remits with no candidates above the threshold.
+- **Done today** — terminal state transitions in the last 24 hours.
+
+The page subscribes to the SP5 claim and remittance tail streams
+(`/api/claims/stream` and `/api/remittances/stream`); a new `item`
+event refetches the lane payload (debounced ~250ms). When a 999
+parses and rejects claims, the inbox reflects the new
+**Rejected** rows within a fraction of a second.
+
+### Inbox endpoints
+
+| Method | Path                                          | Notes                                                            |
+| ------ | --------------------------------------------- | ---------------------------------------------------------------- |
+| GET    | `/api/inbox/lanes`                            | All four lanes in one call.                                      |
+| POST   | `/api/inbox/candidates/{remit_id}/match`      | Manual match. `409` if the claim state moved out from under us.  |
+| POST   | `/api/inbox/candidates/dismiss`               | `{pairs: [{claim_id, remit_id}]}`. Session-scoped.               |
+| POST   | `/api/inbox/rejected/resubmit`                | `{claim_ids: [...]}`. `200` with `conflicts` for non-rejected.   |
+| GET    | `/api/inbox/export.csv?lane=<lane>`           | Streams CSV of the lane's rows.                                  |
+
+### Scoring
+
+4-field weighted (sum = 100):
+
+| Field                   | Weight | Rule                                                          |
+| ----------------------- | ------ | ------------------------------------------------------------- |
+| Patient control number  | 40     | Exact match, normalized (case + leading zeros).              |
+| Service date            | 25     | Linear decay over ±3 days.                                    |
+| Charge amount           | 20     | Linear decay over ±10%.                                       |
+| Provider NPI            | 15     | Exact match. Missing → 0.                                     |
+
+Tiers: **strong** (≥75, full opacity, Match enabled), **weak**
+(50–74, dimmed), **hidden** (<50, not surfaced).
+
 ## Persistence
 
 Parsed batches, claims, remittances, matches, and activity events are