Use the real Odoo 19 external API (JSON-2), and batch calls

The previous commit moved to /jsonrpc, which the v19 docs list as deprecated
alongside /xmlrpc — both go away in Odoo 22. The actual v19 external API is
JSON-2: POST /json/2/<model>/<method>, API key as a bearer token.

Three consequences, all of which change calling code:
  - no uid and no password; UID now comes from res.users/context_get
  - every argument is named, positional args do not exist, so x() becomes
    x(model, method, ids=None, **kwargs) and callers pass domain=/vals=/fields=
  - one call is one transaction and nothing chains, which is the mechanical
    reason state changes must go through a button method

Batching: no multi-call envelope exists, so batching means widening a call, not
bundling calls. Added get_or_create_many() (one search_read + one create for a
whole set) and put build_demo.py's product, customer, vehicle, invoice and
headroom loops through set-based calls.

test_odoo_connect.py checks the call shape and the batching offline, with a
faked urlopen — none of this can be exercised without a live instance otherwise.

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

README.md

@@ -44,9 +44,11 @@ same-named fork silently shadows upstream depending on install order.
 
 ## Quickstart
 
-1. Put your Odoo creds in env vars (or `scripts/creds.json`):
-   `ODOO_URL`, `ODOO_DB`, `ODOO_LOGIN`, `ODOO_KEY`.
-2. Verify the connection: `python scripts/odoo_connect.py` → prints `server_version`.
+1. Put your Odoo creds in env vars (or `scripts/creds.json`): `ODOO_URL`, `ODOO_KEY`, and
+   `ODOO_DB` if one domain serves several databases. JSON-2 authenticates on the API key
+   alone — there is no login/password, so no `ODOO_LOGIN`.
+2. Verify the connection: `python scripts/odoo_connect.py` → prints the server version and uid.
+   (`python scripts/test_odoo_connect.py` checks the call shape offline, no server needed.)
 3. Copy `demo_config.example.json` → `scripts/demo_config.json`, fill it from the brief.
 4. Ask Claude to run the pipeline (see [`SKILL.md`](SKILL.md)).
 
@@ -61,8 +63,9 @@ Several core fields were renamed in v19 (`res.users.group_ids`, `res.groups` los
 ```
 SKILL.md                           the procedure (what the agent follows)
 UPSTREAM.md                        fork point + divergence from upstream
-scripts/odoo_connect.py            JSON-RPC connector + helpers
+scripts/odoo_connect.py            JSON-2 connector + helpers
 scripts/build_demo.py              config-driven data + hero builder (template)
+scripts/test_odoo_connect.py       offline self-check of the JSON-2 call shape
 demo_config.example.json           per-client config shape
 reference/odoo19-field-gotchas.md  version-specific fields + footguns
 templates/                         brand.css + the doc templates