refactor(config): one Shield IP field for both transports (t41)

The two address fields were the same Shield spelled twice, and every bug in the
zeroconf/IP-change path came from keeping them in sync. One field now:

* const.CONF_HOST replaces CONF_ADB_HOST / CONF_PROTOCOL_HOST in the setup form,
  the options page, the pairing forms, the reconfigure/reauth seeding and the
  description copy. ADB port 5555 stays the only port field;
* helpers.entry_host(entry) is the single resolver (options first, then data);
  resolve_adb_config and the protocol settings both go through it, so both
  transports read the same value at call time (the t32 F1 factory re-read keeps
  working: the NEXT built poller sees the new address);
* helpers.seed_host / seed_adb_enabled own the YAML seed's shape rule. A block
  may use `host` or the legacy protocol_host/adb_host keys — t41 keeps the old
  spelling working — and t32 F4's outcome is unchanged: a protocol-only block
  leaves ADB off, an address (or an explicit adb_enabled) turns it on;
* the zeroconf IP-change path collapses the t21-F2 per-host dance into one rule:
  the discovery address IS the entry's address, so the entry is updated when it
  differs and left alone when it matches. The blank-self-heal and
  deliberately-different-ADB-host cases are gone with the duplication — a
  second address field cannot express them anymore, and the tests now pin that
  (previously "an explicit override is never clobbered");
* the options page exposes the protocol toggle it never had (the page could turn
  ADB off but not the protocol);
* button.py (granted to this task) reads the entry's own address instead of
  another integration's entity.

The v3 entry migration that maps existing adb_host/protocol_host onto CONF_HOST
and drops the androidtv key lands in the next commit; HA runs migrations before
setup, so an existing entry is never read with the old shape.

Verified: 311 passed / 2 skipped, 312 / 1 with androidtvremote2, ruff clean,
drift engine exit 0 on HEAD. The UI-copy contract tests (every rendered field
has a label in strings.json AND translations/en.json, key trees identical, host
errors name the field) drove the string edits.

tests/test_init.py

@@ -119,8 +119,9 @@ class TestYamlSeedBlocks:
     """_yaml_seed_blocks: the optional domain key → normalized seeds."""
 
     def test_block_normalized(self, _integration_module):
-        from nsh.const import CONF_ADB_HOST, CONF_ADB_PORT, DEFAULT_ADB_PORT
+        from nsh.const import CONF_ADB_PORT, CONF_HOST, DEFAULT_ADB_PORT
 
+        # t41: a LEGACY block (adb_host) still seeds — normalized onto CONF_HOST
         blocks = _integration_module._yaml_seed_blocks(
             [{"name": "Living", "adb_host": "10.0.0.31"}]
         )
@@ -128,20 +129,31 @@ class TestYamlSeedBlocks:
         assert len(blocks) == 1
         seed = blocks[0]
         assert seed["name"] == "Living"
-        assert seed[CONF_ADB_HOST] == "10.0.0.31"
+        assert seed[CONF_HOST] == "10.0.0.31"
         assert seed[CONF_ADB_PORT] == DEFAULT_ADB_PORT
         assert seed["adb_enabled"] is True
         assert "unique_id" not in seed  # optional key only
 
+    def test_the_current_host_key_seeds_too(self, _integration_module):
+        from nsh.const import CONF_HOST
+
+        seed = _integration_module._yaml_seed_blocks(
+            [{"name": "Desk", CONF_HOST: "shield.local"}]
+        )[0]
+
+        assert seed[CONF_HOST] == "shield.local"
+        assert seed["adb_enabled"] is True  # an address names the Shield
+
     def test_single_block_and_protocol_hint(self, _integration_module):
         blocks = _integration_module._yaml_seed_blocks(
             {"name": "Desk", "protocol_host": "shield.local", "adb_port": 5000}
         )
 
         assert len(blocks) == 1
-        # protocol fields are prefill hints ONLY (pairing stays interactive)
-        assert blocks[0]["protocol_host"] == "shield.local"
+        # a legacy protocol-only block still seeds, with ADB left OFF (t32 F4)
+        assert blocks[0]["host"] == "shield.local"
         assert blocks[0]["adb_port"] == 5000
+        assert blocks[0]["adb_enabled"] is False
 
     def test_list_and_single_block_shapes(self, _integration_module):
         single = _integration_module._yaml_seed_blocks({"name": "A"})
@@ -166,7 +178,23 @@ class TestSeeding:
         domain, context, data = hass.config_entries.flows[0]
         assert domain == "nvidia_shield"
         assert context["source"] == "import"
-        assert data["adb_host"] == "10.0.0.5"
+        assert data["host"] == "10.0.0.5"  # t41: one address field
+
+
+class TestSeedingCurrentKey:
+    """The t41 `host` key seeds exactly like the legacy one."""
+
+    async def test_host_key_seeds_a_flow(self, _integration_module):
+        hass = _SeedHass(entries=[])
+
+        await _integration_module.async_setup(
+            hass, {"nvidia_shield": [{"name": "H", "host": "10.0.0.7"}]}
+        )
+        if hass.scheduled_tasks:
+            await asyncio.gather(*hass.scheduled_tasks, return_exceptions=True)
+
+        assert len(hass.config_entries.flows) == 1
+        assert hass.config_entries.flows[0][2]["host"] == "10.0.0.7"
 
     async def test_hostless_block_never_seeds(self, _integration_module):
         hass = _SeedHass(entries=[])
@@ -229,12 +257,12 @@ class TestImportStep:
         return flow
 
     async def test_ui_configured_host_never_re_seeded(self):
-        from nsh.const import CONF_ADB_HOST
+        from nsh.const import CONF_HOST
 
         existing = SimpleNamespace(
             entry_id="ui1",
             unique_id=None,
-            options={CONF_ADB_HOST: "10.0.0.31"},
+            options={CONF_HOST: "10.0.0.31"},
         )
         # options live on the entry (conf zeroconf guard reads them)
         flow = self._flow([existing])