Add cool-only global RAC support: WindFree, Auto mode, display light

Finishes PR #91's contribution (pedroperosin) with the requested review
changes applied, on our own branch:

- Preset resolution is now fully dynamic, read from each unit's own
  /mode/convenient/vs/0 supportedModes instead of a static per-model
  table -- any board's convenient modes (including WindFree's Nano/
  NanoSleep) surface without code changes. Unlabelled codes across
  existing fixtures (longwind, motionindirect, motiondirect, drycomfort)
  plus the two new WindFree ones are added to en.json/nl.json.
- 'Auto' now maps to HVACMode.AUTO instead of HEAT_COOL: these are
  single-setpoint "device decides" units, not two-setpoint heat+cool
  ones. 'Fan' is added alongside 'Wind' as a second FAN_ONLY spelling;
  a new _device_code_for_hvac() picks the code from the unit's own
  supportedModes since the flat map can't disambiguate two device codes
  mapping to one HA value.
- Detection gains a hyphenated '-RAC-' modelNum fallback (alongside the
  existing '_RAC_') for cool-only global RAC variants whose
  /otninformation/vs/0 ships no swVersionInfo block.
- Adds a display_light switch sourced from /mode/vs/0's opaque options
  blob (inverted Light_On/Light_Off token) for boards with no dedicated
  /light/vs/0 switch.

Write-path behavioural change (touches the path iterated on across
#9/#17/#27/#38/#54): power now targets the vendor /power/vs/0 instead of
the OCF /power/0, and _is_on() reads vendor-first. /power/0 is absent on
several known AC boards, so the previous OCF-first read/write pair could
report and act on stale state -- consistent with #53's "can turn on but
not off". Target temperature now picks its channel (OCF pair vs. vendor
items[]) based on which the unit actually reports, reading and writing
the same one.

The vendor temperature write and the new display-light write both carry
only the changed field(s), not the whole resource -- confirmed sufficient
on the wire, the device merges the rest itself. That requires the
coordinator's optimistic cache to do the same merge on the read side so a
setpoint change doesn't blank out current/min/max/unit for the settle
window: common.py gains merge_items_field() next to the existing
merge_options_field(), and async_send_command wires it in for any write
touching x.com.samsung.da.items.

New fixture/golden for the cool-only global RAC variant (TP1X_DA-AC-RAC-
01001, AI_RAC_GLOBAL_COOLONLY_3.0); display_light added to the goldens
for boards that gain the new options-based switch. Regenerated against
current main rather than copied from the original PR, since those
goldens had already shifted (current_temperature_c/humidity from issue
#75).

tests/test_common_capabilities.py

@@ -59,6 +59,42 @@ class TestMergeOptionsField:
         assert common.merge_options_field(cached, ['nounderscore']) == ['Course_16']
 
 
+class TestMergeItemsField:
+    """merge_items_field() is the items[]-array counterpart of
+    merge_options_field above (issue #91 review feedback): a vendor
+    x.com.samsung.da.items[] write only needs to carry the item id plus the
+    field(s) being changed, so the coordinator uses this to keep its
+    optimistic cache entry complete (current/minimum/maximum/unit still
+    present) without waiting on a real poll."""
+
+    def test_merges_fields_into_matching_id(self):
+        cached = [{'x.com.samsung.da.id': '0', 'x.com.samsung.da.current': '20.0',
+                   'x.com.samsung.da.maximum': '30', 'x.com.samsung.da.minimum': '16'}]
+        merged = common.merge_items_field(
+            cached, [{'x.com.samsung.da.id': '0', 'x.com.samsung.da.desired': '22'}])
+        assert merged == [{'x.com.samsung.da.id': '0', 'x.com.samsung.da.current': '20.0',
+                            'x.com.samsung.da.maximum': '30', 'x.com.samsung.da.minimum': '16',
+                            'x.com.samsung.da.desired': '22'}]
+
+    def test_appends_when_id_absent(self):
+        cached = [{'x.com.samsung.da.id': '0', 'x.com.samsung.da.current': '20.0'}]
+        merged = common.merge_items_field(
+            cached, [{'x.com.samsung.da.id': '1', 'x.com.samsung.da.desired': '22'}])
+        assert merged == [
+            {'x.com.samsung.da.id': '0', 'x.com.samsung.da.current': '20.0'},
+            {'x.com.samsung.da.id': '1', 'x.com.samsung.da.desired': '22'},
+        ]
+
+    def test_handles_missing_cache(self):
+        assert common.merge_items_field(
+            None, [{'x.com.samsung.da.id': '0', 'x.com.samsung.da.desired': '22'}]
+        ) == [{'x.com.samsung.da.id': '0', 'x.com.samsung.da.desired': '22'}]
+
+    def test_ignores_malformed_new_items(self):
+        cached = [{'x.com.samsung.da.id': '0', 'x.com.samsung.da.current': '20.0'}]
+        assert common.merge_items_field(cached, ['not-a-dict']) == cached
+
+
 # ---------------------------------------------------------------------------
 # OCF-native / vendor '-vs' fallback pairs (power, kids-lock, remote control).
 # ---------------------------------------------------------------------------