feat: promote linux native audio path

poc/tsclientlib-filetransfer-spike/VERIFICATION.md

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+# Verification record — `tsclientlib-filetransfer-spike`
+
+## Result
+
+PASS. The spike successfully downloaded a real file from
+`kr.teamspeak.app` over the TeamSpeak fileserver path.
+
+## Environment
+
+| Field | Value |
+|---|---|
+| Date | 2026-05-25 |
+| Host OS | Linux (x86_64) |
+| Build profile | dev |
+| Target server | `kr.teamspeak.app` |
+
+## Command
+
+```bash
+cargo run --offline -- \
+  --address kr.teamspeak.app \
+  --nickname ChanoraPoC-Downloader
+```
+
+## What was observed
+
+- `ftgetfilelist` against visible channel IDs did not return typed file rows on
+  this server; each scan attempt failed with `ParameterNotFound`.
+- The fallback logic selected `EdisonJwa`'s avatar path:
+  - channel id: `0`
+  - remote path: `/avatar_ebmjofhfgojajpappiikgponphiippbficbmfemf`
+- `download_file` completed successfully.
+- Reported file size: `129453`
+- Copied bytes: `129453`
+- Saved artifact:
+  - `downloads/avatar_ebmjofhfgojajpappiikgponphiippbficbmfemf`
+
+## Conclusion
+
+The practical TeamSpeak fileserver download path is proven:
+
+1. determine a valid TeamSpeak remote path,
+2. request the transfer bootstrap,
+3. open the returned file-transfer TCP stream,
+4. receive raw bytes and persist them locally.