Update README for Phase 4 Slack surfaces

README.md

@@ -84,8 +84,8 @@ docs/BUILD.md            phased, end-to-end build guide
 
 | Where | What |
 |---|---|
-| **Secrets Manager** | `apm-wo-analysis/anthropic-api-key` (Haiku fallback). Slack bot token reused from the `payments-dashboard` app. |
-| **SSM Parameter Store** | operational config (Slack channel ID, schedule expressions, deep-link base URL). |
+| **Secrets Manager** | `apm-wo-analysis/anthropic-api-key` (Haiku fallback); `apm-wo-analysis/slack-credentials` = `{ botToken, signingSecret, channelId }` (reused Slack app). |
+| **SSM Parameter Store** | `/apm-wo-analysis/grafana-base-url` (the 📊 dashboard button / modal overflow link; ops-editable). |
 | **GitHub repo secret** | `AWS_DEPLOY_ROLE_ARN` — the OIDC deploy role `githubdeploy-apm-wo-analysis`. |
 
 No secrets in Lambda environment variables.
@@ -142,7 +142,7 @@ cdk deploy apm-wo-analysis-grafana    # EC2, ALB, SG, Route53, datasource role
 
 ## Status
 
-**Phase 3 — analytics dataset (in review).** Build-out proceeds per
+**Phase 4 — Slack surfaces (in review).** Build-out proceeds per
 [`docs/BUILD.md`](./docs/BUILD.md): ingestion → classifier → Glue/Athena → Slack
 → Grafana → docs.
 
@@ -155,4 +155,8 @@ cdk deploy apm-wo-analysis-grafana    # EC2, ALB, SG, Route53, datasource role
   implemented and `cdk synth`-green; PR #9 open (stacked on Phase 2). The
   classifier writes pure Parquet and holds no Glue access (projection handles
   partitions).
-- **Phases 4–6** (Slack, Grafana, final docs) — not started.
+- **Phase 4** Slack post + interactions Lambdas (daily summary, batched
+  3rd-escalation alert, drill-down modals on `apm-wo.seahaven.com`) — implemented
+  and `cdk synth`-green; PR #10 open (stacked on Phase 3). App manifest in
+  `slack/manifest.yaml`.
+- **Phases 5–6** (Grafana, final docs) — not started.