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/gamepad.rs

@@ -1493,7 +1493,7 @@ impl Worker {
             Err(e) => {
                 tracing::warn!(pad = slot.index, low, high, error = %e, "rumble: SDL set_rumble failed")
             }
-            Ok(()) => tracing::debug!(pad = slot.index, low, high, "rumble: rendered"),
+            Ok(()) => tracing::trace!(pad = slot.index, low, high, "rumble: rendered"),
         }
         slot.rumble.last = (low, high);
         slot.rumble.last_at = Some(Instant::now());