news-digest/README: document multi-tenant onboarding + per-user cron

Adds a "Customizing the run schedule" section (DIGEST_CRON_AM/PM env
vars, edit-and-recreate flow) and a "Multi-tenant: one instance per
teammate" section covering scripts/add-digest-user.sh end to end:
what it does, the per-user file layout on ana-docker, idempotent
schedule/password updates, and the teardown path.

Updated the stale "two editions per day" intro line to note the
schedule is now configurable.

stacks/news-digest/README.md

@@ -27,8 +27,10 @@ noisy. This stack:
    (state in `/output/hidden.json`, shared across every device the
    user opens the digest from).
 
-Two editions per day: 8am and 8pm local. Plus per-edition archives
-at `/edition-YYYY-MM-DD-{am,pm}.html`.
+Two editions per day by default (0800 / 2000 local), parametrized via
+`DIGEST_CRON_AM` / `DIGEST_CRON_PM` env so each per-user instance can
+fire on its own schedule. Plus per-edition archives at
+`/edition-YYYY-MM-DD-{am,pm}.html`.
 
 ## Architecture
 
@@ -127,12 +129,133 @@ with tool/JSON-mode support give better summarization quality;
 ## Forcing a fresh digest now
 
 ```bash
-ssh ana-docker 'docker exec news-digest-worker python3 /app/digest.py'
+ssh ana-docker 'docker exec news-digest-worker /usr/local/bin/run-digest.sh'
 ```
 
 Runs the full pipeline once, ignoring cron. Useful after changing
 filtering knobs or adding feeds.
 
+## Customizing the run schedule
+
+Times come from two env vars on the worker, written into the busybox
+crontab at container start. Standard 5-field cron syntax.
+
+| Var | Default | Effect |
+|---|---|---|
+| `DIGEST_CRON_AM` | `0 8 * * *` | morning fire |
+| `DIGEST_CRON_PM` | `0 20 * * *` | evening fire |
+
+`busybox crond` honors `$NEWS_DIGEST_TZ` (defaults to
+`America/Los_Angeles`), so values are interpreted in the configured TZ.
+
+```bash
+# Shift the canonical instance to 7am / 6pm
+ssh ana-docker '
+  cd /opt/docker/compose/news-digest
+  sed -i "s|^DIGEST_CRON_AM=.*|DIGEST_CRON_AM=0 7 * * *|" .env
+  sed -i "s|^DIGEST_CRON_PM=.*|DIGEST_CRON_PM=0 18 * * *|" .env
+  docker compose up -d --force-recreate news-digest-worker
+'
+```
+
+Verify the rendered crontab:
+
+```bash
+ssh ana-docker 'docker exec news-digest-worker cat /etc/crontabs/root'
+```
+
+## Multi-tenant: one instance per teammate
+
+Architecture: **shared miniflux + per-user digest stack**. Miniflux
+already supports multi-user natively (each user has their own feeds,
+categories, hide-state); we layer a separate news-digest stack per
+user on its own port + output dir, scoped to that miniflux user's
+credentials.
+
+### Onboarding a new user
+
+```bash
+# Defaults — 8am / 8pm local, random password
+scripts/add-digest-user.sh alice
+
+# Custom hours
+scripts/add-digest-user.sh bob --am "0 6 * * *" --pm "0 17 * * *"
+
+# Weekday-only PM run
+scripts/add-digest-user.sh carol --pm "30 18 * * 1-5"
+
+# Pin a known password (still creates the miniflux user if missing)
+scripts/add-digest-user.sh dan 'pickyourpassword' --am "0 9 * * *"
+```
+
+What the script does:
+
+1. Reads miniflux admin creds from
+   `ana-docker:/opt/docker/compose/miniflux/.env`.
+2. Allocates the next free `NEWS_DIGEST_PORT` (scans existing
+   `news-digest` + `digest-*` `.env` files).
+3. Creates the miniflux user via the admin API. Already-exists is
+   non-fatal (kept; password not reset).
+4. Provisions per-user dirs at
+   `/opt/docker/compose/digest-<user>/` and
+   `/opt/docker/data/digest-<user>/` (one-time sudo prompt — the
+   script falls back to printing the manual command if there's no TTY).
+5. Materializes a per-user `.env` (inherits `NEWS_DIGEST_TAG` from the
+   canonical stack so all tenants run the same image).
+6. Brings the stack up via `docker compose -p digest-<user> up -d`.
+7. Runs `seed-headlines.py` against miniflux as the new user (creates
+   the World + Local categories with default feeds).
+8. Triggers a first digest run so the page isn't blank.
+
+Outputs the digest URL, miniflux login, and rendered cron schedule.
+
+### Per-user file layout
+
+```
+ana-docker:
+  /opt/docker/compose/digest-<user>/   # compose + .env + build context
+    .env                               # auto-generated, contains MINIFLUX_PASSWORD
+    compose.yaml
+    Dockerfile + digest.py + ...       # build context (image is shared/cached)
+  /opt/docker/data/digest-<user>/      # rendered HTML + per-user hidden.json
+    index.html
+    edition-YYYY-MM-DD-{am,pm}.html
+    hidden.json
+    .article-cache.json                # extracted article text, 7-day TTL
+```
+
+Container names: `digest-<user>-worker` and `digest-<user>-web`.
+
+### Updating an existing user's schedule
+
+Re-running the script with the same username is idempotent:
+
+```bash
+# Change alice's evening run to 5:30pm
+scripts/add-digest-user.sh alice --pm "30 17 * * *"
+```
+
+The miniflux user is kept (password unchanged), the .env is
+re-materialized with the new schedule, and the worker container is
+recreated. Use the same flow to bump cron times, rotate passwords
+(by passing a new one explicitly), or rerun feed seeding.
+
+### Removing a user
+
+```bash
+ssh ana-docker '
+  cd /opt/docker/compose/digest-alice
+  docker compose -p digest-alice down -v
+'
+# Optional: nuke compose dir + rendered output
+ssh -t ana-docker 'sudo rm -rf /opt/docker/compose/digest-alice /opt/docker/data/digest-alice'
+# Optional: delete the miniflux user via the admin UI at http://10.250.50.70:8080/
+```
+
+The digest is gone immediately; the miniflux account stays around
+unless you delete it explicitly (cheap to leave; ~zero resource cost
+when no stack is querying its feeds).
+
 ## Logs
 
 ```bash