fix(tests): un-nest AudioMetaUtilsTest — the whole class never ran

[PonceGL]

What

app/src/test/.../utils/AudioMetaUtilsTest.kt is corrupted by what looks like
a bad paste or merge: mimeTypeToFormat_mapsUniversalFormats is defined three
times — once at class level, and twice more as local functions nested inside
mimeTypeToFormat_mapsM4aVariants and mimeTypeToFormat_mapsSamsungFormats.
One of the small independent fixes listed in #2813.

Braces are balanced (Kotlin allows local functions), so it compiles. But a
local function carrying @Test compiles to a synthetic
exterior$interior method, and JUnit4's runner rejects the whole class for
it: InvalidTestClassError: ... should not be static / should be public.

The real cost: the class never runs at all. mimeTypeToFormat() — used on
every library scan — has had zero test coverage since this landed, silently.

Change

Un-nests the three functions back to class level, three @Test methods, no
class-level duplication. Not a single assertion changed — I checked all 16
by hand against the current mimeTypeToFormat() implementation: they were
already correct, they just never ran. First real execution, all green.

Testing

The fix is the test result: 3 tests that previously errored on
class-load now pass. :app:testDebugUnitTest — 390 tests, only the 4
other pre-existing baseline failures remain, none new.

[PonceGL]

Closing for now — reorganizing how this work is staged. It'll go through our fork first and we'll propose it upstream again, possibly bundled differently, once the larger feature it's part of is further along. Not a rejection, just a process change on our side.