Update README and saltire docs to current behavior

The README now documents the daily workflow (working date, live mode
vs printed lists, regenerate semantics, full day-editor editability),
describes cycle mode's rolling rotation accurately, repairs the
custom-parameters section, and points to the saltire testing guide,
which gains resume-after-a-break instructions.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docs/SALTIRE.md

@@ -69,6 +69,34 @@ On https://saltire.lti.app → Test Platform → **Security Model**:
    `http://purl.imsglobal.org/vocab/lis/v2/membership#Learner`, save,
    and Connect again — you land on /me.
 
+## Picking the test setup back up
+
+With the configuration saved under a saltire account (sign in, then
+Save), resuming a test session is short:
+
+1. Start the local server (the keys and TLS cert in `instance/` are
+   already there):
+
+   ```
+   COLDCALL_SECRET_KEY=saltire-test .venv/bin/python -m flask \
+       --app coldcall_lti run --port 5443 \
+       --cert instance/tls-cert.pem --key instance/tls-key.pem
+   ```
+
+2. If the browser has forgotten the self-signed certificate, open
+   https://localhost:5443/healthz and click through the warning again.
+3. Sign in at https://saltire.lti.app → Test Platform, confirm the
+   saved configuration loaded (Security Model should show LTI 1.3 and
+   the localhost URLs), and press **Connect**.
+4. If the launch fails at JWT validation or roster sync, compare the
+   token/jwks URLs shown in Platform Details against
+   `instance/lti_config.json` — the session id may have changed; copy
+   the new values in. Everything else should be stable.
+
+To test as a student instead of the instructor, change the role under
+**User** to `.../membership#Learner`, Save, and Connect; switch back
+to `#Instructor` the same way.
+
 ## Caveats
 
 - **The token and jwks URLs embed a saltire session id** (the