chore: consolidate parallel-session WIP (HOLD — do not push)

Local snapshot of intermingled in-flight work, committed to unblock the encode
refactor (a clean ffmpeg_win.rs for the vbv-dedup follow-on). These hunks span
the same files and can't be cleanly split here; the commit bundles three
distinct workstreams that each belong in their own PR:

  - logging rework (~43 files: level re-tiering, structured fields, `?e`,
    hot-path flood latches)
  - conflicting-host detection (detect.rs + detect/{linux,windows}.rs + wiring
    in main.rs/mgmt.rs/Cargo.toml/docs/packaging)
  - standby-sink DWM-stall attribution (windows/display_events.rs + capture/
    vdisplay wiring)

NOT verified as a combination. NOT to be pushed until the refactor is done and
these are re-verified and reorganized into their proper per-workstream PRs.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

crates/punktfunk-host/src/audio/windows/wasapi_cap.rs

@@ -39,7 +39,7 @@ impl WasapiLoopbackCapturer {
             .name("punktfunk-wasapi-audio".into())
             .spawn(move || {
                 if let Err(e) = capture_thread(tx, stop_t, ready_tx, channels) {
-                    tracing::error!(error = format!("{e:#}"), "wasapi loopback thread failed");
+                    tracing::error!(error = %format!("{e:#}"), "wasapi loopback thread failed");
                 }
             })
             .context("spawn wasapi audio thread")?;