Fix bounded Opus packet-loss concealment in embedded Linux audio

[zortos293]

Changes

Preserve the sender SSRC and RTP timestamp through the embedded Linux audio handoff. Measure unrecovered loss from the RTP timeline and synthesize Opus concealment in valid sample chunks, capped at 100 ms and the existing PCM buffer capacity.

Reset Opus state when the sender source changes. Carrying the SSRC on every packet preserves this reset even if a bounded queue drops the first packet from the new source. RED-recovered packets are decoded normally without duplicate concealment.

Verification

Independently reviewed the final diff and reran:

• Linux audio tests against real libopus: 19 passed, with 2 existing device-dependent tests ignored.
• Audio transport regressions: 11 passed.
• Full native streamer workspace tests: all passed, including 192 transport and 102 Linux platform tests.
• Workspace formatting and Clippy: passed.

Regressions cover RTP wrap, short and burst losses, varying packet durations, backward timestamps, source reset, a dropped first packet after source change, and RED recovery.

Limits

No live GFN session, hardware decode, or real playback-device packet-loss test was available. The evidence is transport and real-libopus regression testing, not live gameplay validation. Audio-only failure isolation is a separate dependent change. No UI or FFI ABI changes.

[coderabbitai]

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[capy-ai]

Capy found no issues.

View 2 other findings in Capy.

[capy-ai]

Review replacement: #959. This PR was marked merged when a dependent task accidentally pushed directly to dev. The user authorized repair, and dev has now been restored to 7a76b0c965087750d46411901ce8d04ba1b2524a with an exact force-with-lease. The unchanged PLC commit is preserved on capy/linux-opus-plc-review and requires review through #959. Audio failure isolation is separately stacked in #960. The historical merged status here is not evidence that these changes are currently on dev.