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/vdisplay/linux/gamescope.rs

@@ -1278,7 +1278,7 @@ fn launch_session(client: &str, unit_name: &str, mode: Mode) -> Result<u32> {
         // and the transient unit has no Restart= — without supervision the rest of this poll would
         // wait on a corpse. Re-run the unit so every readiness attempt inside the deadline is used.
         if !unit_starting_or_active(unit_name) {
-            tracing::info!(
+            tracing::warn!(
                 unit = unit_name,
                 "gamescope session: transient unit died (missed the wrapper's 5 s gamescope \
                  readiness window?) — relaunching"

crates/punktfunk-host/src/vdisplay/linux/kwin.rs

@@ -685,7 +685,7 @@ fn run(
             .dispatch_pending(&mut state)
             .context("dispatch_pending")?;
         if state.closed {
-            tracing::warn!("KWin closed the virtual-output stream");
+            tracing::warn!(output = %name, node_id, "KWin closed the virtual-output stream");
             break;
         }
         conn.flush().context("wayland flush")?;

crates/punktfunk-host/src/vdisplay/linux/mutter.rs

@@ -255,12 +255,12 @@ fn session_thread(
             Ok(dc) => match get_state(&dc).await {
                 Ok(state) => Some((dc, state)),
                 Err(e) => {
-                    tracing::warn!("mutter: GetCurrentState (pre) failed ({e:#}); topology + scale persistence off");
+                    tracing::warn!(error = %format!("{e:#}"), "mutter: GetCurrentState (pre) failed; topology + scale persistence off");
                     None
                 }
             },
             Err(e) => {
-                tracing::warn!("mutter: DisplayConfig unavailable ({e:#}); topology + scale persistence off");
+                tracing::warn!(error = %format!("{e:#}"), "mutter: DisplayConfig unavailable; topology + scale persistence off");
                 None
             }
         };
@@ -301,14 +301,16 @@ fn session_thread(
                                 if exclusive { "disabled" } else { "kept" }
                             ),
                             Err(e) => tracing::warn!(
-                                "mutter: could not set the virtual output primary ({e:#}); streaming continues — the desktop may render on the physical monitor"
+                                error = %format!("{e:#}"),
+                                "mutter: could not set the virtual output primary; streaming continues — the desktop may render on the physical monitor"
                             ),
                         }
                     }
                     tracked = Some((dc, pre, vconn));
                 }
                 Err(e) => tracing::warn!(
-                    "mutter: virtual connector not identified ({e:#}); topology + scale persistence off"
+                    error = %format!("{e:#}"),
+                    "mutter: virtual connector not identified; topology + scale persistence off"
                 ),
             }
         }
@@ -737,7 +739,8 @@ async fn make_virtual_primary(
                 tracing::warn!(
                     scale,
                     derived,
-                    "mutter: ApplyMonitorsConfig at the remembered scale failed ({e:#}); retrying at the derived scale"
+                    error = %format!("{e:#}"),
+                    "mutter: ApplyMonitorsConfig at the remembered scale failed — retrying at the derived scale"
                 );
                 scale = derived;
             }