test(discovery): fixtures for the parsers, the bounded sweep and the surfaces

tests/test_installed_apps.py is new and is where the discovery claims are
pinned. NO REAL SHIELD WAS AVAILABLE, so the command output is fixture-based
in the documented Android shapes — `pm list packages` lines, the verbose
`resolve-activity` header followed by `package/activity`, and `pm dump`
carrying `application-label` — including a localized label (the default
locale wins), a label-less app (a definitive negative, and still a row) and
the launcher (a system app that must be present).

Covered: both parsers plus their tolerances (noise, duplicates, blank,
a bare `package/activity` line, the settings entry point that is not a
launcher), the user+launcher merge and its de-duplication, the icon
heuristic and that it is always a string, the sweep's commands, its
concurrency bound (peak <= APP_SWEEP_CONCURRENCY and > 1, so it is bounded
AND genuinely concurrent), cache reuse with zero shells, the TTL, shared
sweeps for concurrent callers, and every degradation path (no poller,
disconnected, mute transport — empty list, no loop, no raise). The sensor's
count/table/reason and the "a failed refresh is a no-op, not an exception"
behaviour are pinned too.

The config-flow side is in tests/test_config_flow_ux.py: the table lists
every discovered app, a discovered app the map never mentions is appended,
the user's name wins for the same package, an `mdi:` value never reaches the
icon column, rendering issues no shell, the Discover row runs one forced
sweep and returns to the menu, a failed sweep still renders, and the merged
table round-trips into the saved options.

Also: tests/test_config_flow_real_ha.py learns the new row, the standalone
stub accepts `description_placeholders` (which the apps form now passes),
and the state=6 wording in media_session.py/media_player.py is the t57
UNIT 0c reword.

tests/test_config_flow_real_ha.py

@@ -219,6 +219,7 @@ class TestRealMenuFlow:
             "connection",
             "receiver",
             "apps",
+            "discover",
             "scripts",
             "finish",
         }
@@ -229,7 +230,8 @@ class TestRealMenuFlow:
         # each row is opened on its own flow, because a real flow keeps ONE
         # step at a time — reopening from a fresh menu is what the browser does
         for row in menu["menu_options"]:
-            if row == "finish":
+            if row in ("finish", "discover"):
+                # actions: `finish` commits and `discover` sweeps, neither renders
                 continue
             _manager, fresh = await open_options(ha, entry)
             opened = await _manager.async_configure(