v3.0.0rc1

Added

• Discard queued playback on TX streams (MOR-3760). TxStream and
  DuplexStream gain async discard_queued(), dropping every playback
  frame queued but not yet handed to the device and returning how many
  queued writes were dropped; TxStreamHealth reports discard_events
  and discarded_audio_ms.
• Outside-only TX audio admission (MOR-3764). New binary TX frame type
  0x12 on /api/v1/audio: admitted only while the radio is observed keyed
  outside Core (intent rx, no release debt, a foreign TX observation),
  authorized and pushed atomically against any Core-client keying
  transition; refused otherwise. 0x11 behavior is unchanged.

Fixed

• Profile receive ranges match published coverage (MOR-3782). The
  IC-7300MK2, IC-705 and FTX-1 profiles' tuning/receive ranges now match
  the manufacturer's published receiver coverage (IC-7300MK2 up to
  74.800 MHz; IC-705 0.030-199.999999 and 400-470 MHz; FTX-1 0.030-174
  and 400-470 MHz); no transmit band was added or widened; not verified
  on radios.

• IC-7300 frequency entry and tuning are no longer capped at 60 MHz
  (MOR-3782). The profile now covers the receiver range up to 74.800 MHz,
  which includes the 4 m band; no 4 m transmit band is declared, so the
  frontend does not offer TX at 70 MHz (EU 4 m transmit needs per-radio
  variant selection, a separate follow-up); not verified on a radio.

• IC-7300MK2 CI-V identity (MOR-3792). The shared serial identity
  table now maps the MK2's default CI-V address 0xB6 to IC-7300MK2,
  so identify_radio — and the CI-V identity resolver Pro consumes —
  answers IC-7300MK2 instead of Unknown (0xB6). The MK2 model-ID
  bytes are not documented in the CI-V guide and the radio has not been
  verified on hardware; the profile's identity gate stays unverified.

• Split-mode read-modify-write detects concurrent commands
  (MOR-3743). A split-mode mode write that preserves DATA or filter
  (DualRxRuntimeMixin.write_relative_vfo_mode, rigctld X) now runs
  its preservation read → SET → readback inside an
  IcomCommander.interference_scope: any non-BACKGROUND command
  dispatched by another task between the preservation read and the SET —
  including a direct raw CI-V transaction, which reaches the wire
  without entering the commander queue — marks the scope, the SET is
  refused before the wire (the refusal carries the new
  StaleBeforeWireError, a ConnectionError subclass and the only
  retryable one), and the whole write retries from the preservation
  read — up to three attempts, then a retryable CommandError. A SET
  that already reached the wire is never retried: a currency failure
  raised behind the send — interference detected while the SET's ACK
  was pending — propagates as ConnectionError instead of repeating
  the SET, interference behind an acknowledged SET is decided by the
  readback (a consistent readback succeeds, a contradictory one fails),
  and a VFO selection change during the write — including one that
  completes during the readback — fails it with CommandError even
  though the SET was already applied; the caller must re-read. A
  retired scope's currency dies with it, so a delayed transport
  retransmit request for its SET is answered with the idle packet,
  never the stale tuple. No command is ever delayed or reordered and no
  send priority changed; TX releases are unaffected. This detects and
  retries; it does not exclude anyone.