Advertise the formats in preference order

[chrisuthe]

Why

supported_formats() built the advertisement in the order the device is probed
in — PROBE_RATES and PROBE_BIT_DEPTHS both run ascending — so the list went
out with 22050 Hz / 8-bit at the front.

That order is load-bearing. The spec has supported_formats in priority order,
first preferred, and servers read it that way: aiosendspin's
PlayerRole._ensure_preferred_format() takes filter_encodable_formats(...)[0]
and never looks further. So on any device permissive enough to accept the whole
ladder — the ALSA default PCM in particular, which on a PipeWire or PulseAudio
host converts rather than refuses — Music Assistant settled on FLAC 2 ch
16-bit @ 22050 Hz and stayed there. (16-bit rather than 8-bit only because the
server drops the 8-bit entries itself: FLAC_BIT_DEPTHS = {16, 24, 32}.)

The set was never the problem. The order was.

What changed

supported_formats() returns exactly the same entries, permuted, ranked on
three named ladders:

axis	order	why
codec	FLAC, OPUS, PCM	lossless first; Opus is the fallback worth having where bandwidth is the constraint; PCM costs the most bytes for no gain over FLAC
rate	48000, 44100, 96000, 88200, 192000, 176400, 32000, 22050	48 kHz leads so the preferred rate is also the one rate Opus can be carried at, and the ladder stays in that family; the two rates below CD go last
depth	16, 24, 32, 8	16-bit is what most streams are mastered at; 8-bit can never lead

A permissive device now leads with FLAC 2 ch 16-bit @ 48 kHz, and one that takes
neither 48 nor 44.1 kHz falls through to its best remaining rate rather than
its lowest.

The startup digest reads as the ranking it describes:

I audio: Advertising 65 formats for 'null': FLAC 2ch 16/24/32/8-bit @ 48000/44100/96000/88200/192000/176400/32000/22050 Hz; OPUS 2ch 16-bit @ 48000 Hz; PCM 2ch 16/24/32/8-bit @ 48000/44100/96000/88200/192000/176400/32000/22050 Hz

Ordering only, never narrowing

Dropping entries would be the easy way to force a default, and it would be
wrong: the same advertised list is what Music Assistant builds its per-player
Preferred format menu from, so narrowing it takes choices away from anyone
picking by hand.

The ranking is a std::stable_sort keyed on ladder position, which is a
permutation by construction — it cannot add or drop an entry — and a rate or
depth outside PROBE_RATES/PROBE_BIT_DEPTHS sorts to the back rather than
disappearing. SupportedFormats.RankingOnlyPermutesWhatIsAdvertised holds that
against a spelled-out copy of the old ascending crossing, over ten capability
sets including the degenerate ones.

Tests

New, alongside that permutation test:

• ThePermissiveSetLeadsWithFlacStereo48kHz16Bit
• ADeviceWithNeitherPreferredRateLeadsWithItsBestRemaining ({22050, 96000})
• RatesAndDepthsGoOutRanked
• OpusSitsAfterEveryFlacEntryAndBeforeEveryPcmEntry
• ARateTheLaddersDoNotNameIsAdvertisedLastRatherThanDropped

DescribeFormats.GroupsTheAxesPerCodec followed the old positional order and is
updated — it now also asserts the codec groups appear in ranked order, which it
did not check before.

ctest is 354/354 green with -DSENDSPIN_CLI_BUILD_TESTS=ON -DSENDSPIN_CLI_WERROR=ON, the same configure line CI uses.