Catalog: move emit keys and DER types to data model v2

[davmoz]

Problem

The catalog emits pre-v2 names. The data model is now v2 (srcful-data-models 2.3.0), and no catalog driver emits a v2 key yet. Counted over drivers/lua/*.lua on main (224c438), by number of drivers that assign the key:

Spelling	Examples (drivers)	v2 name
data-models 1.x	W (42), Hz (23), L1_V (24), total_import_Wh (20), SoC_nom_fract (12)	W_ac / W_dc, Hz, l1_V_ac, total_import_Wh_ac, soc_nom_fract
catalog short names	w (52), l1_v (45), hz (37), import_wh (29), soc (21)	as above
v2	W_ac, W_dc, soc_nom_fract, l1_V_ac, total_import_Wh_ac: 0

DER types emitted: meter 55, battery 33, pv 32, v2x_charger 16, ev 6, inverter 4, vehicle 4. In v2, pv is solar and v2x_charger is ev_charger_port. inverter is the inverter's AC output stage only: its DC side is the solar and battery DERs.

spec/host-api-profile.json already counts the lowercase names as debt against the 1.x spellings. That target has since moved to v2.

What the catalog needs

1. One key set: the v2 names, with _ac / _dc on every W/V/A/VA/Wh field. A battery's own measurement is DC. Use the v2 DER types. The field lists per type are in the data model REFERENCE.
2. Null, never 0: a value that was not read stays nil (44 drivers emit numbers they never read (null, never 0) #169, ratcheted by test_no_invented_numbers.py).
3. make: the lowercase brand (^[a-z0-9]+(_[a-z0-9]+)*$, for example abb, sma, carlo_gavazzi), set by the driver itself.
4. Order: FTW Core has to accept the v2 keys first (Publish data model v2 to NovaCore (json/v2) and accept v2 keys from drivers ftw#1527, telemetry_keys.go). Drivers can then move one at a time, each with a version bump and a BUNDLED_SOURCE.json pin move in FTW.
5. Spec: update spec/host-api.md / spec/host-api-profile.json to v2 as the target. docs(spec): describe srcful-data-models v2 in the migration note #166 already rewrites the migration note.

Related: #169 (invented numbers), #170 (zap.lua and the Zap's v2 local API), srcfl/ftw#1527 (FTW's NovaCore publisher and host aliases).

Out of scope for the current data model rollout: tracked here so FTW does not fall behind.

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