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/pf-client-core/src/session.rs

@@ -222,7 +222,7 @@ fn pump(
             preferred = punktfunk_core::quic::CODEC_PYROWAVE;
         } else {
             tracing::warn!(
-                "PUNKTFUNK_PREFER_PYROWAVE=1 but the presenter device failed the pyrowave                  probe — keeping the normal codec preference"
+                "PUNKTFUNK_PREFER_PYROWAVE=1 but the presenter device failed the pyrowave probe — keeping the normal codec preference"
             );
         }
     }
@@ -791,7 +791,7 @@ fn spawn_audio(
                                 buf.extend_from_slice(&pcm[..n]);
                                 player.push(buf);
                             }
-                            Err(e) => tracing::debug!(error = %e, "opus decode"),
+                            Err(e) => tracing::debug!(error = %e, "opus decode failed"),
                         }
                     }
                     Err(PunktfunkError::NoFrame) => {}