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>

docs-site/content/docs/host-cli.md

@@ -86,6 +86,15 @@ hosts from another machine with `punktfunk-probe --discover`. Where multicast do
 Docker/VLAN setups), pass `--no-mdns` (or set `PUNKTFUNK_MDNS=0`) and add the host in the client by
 address instead.
 
+## `detect-conflicts`
+
+`punktfunk-host detect-conflicts` reports other Moonlight-compatible hosts (Sunshine, Apollo, and
+forks) installed or running on this machine. Running one alongside Punktfunk is **unsupported** —
+they fight over the same ports and virtual-display driver. Prints what it found and exits **1** if
+any conflict exists, **0** if clean (so installers and scripts can gate on it). The host also runs
+this check at `serve` startup and surfaces it in the logs, tray, and — on Windows — the installer.
+See [Troubleshooting → another streaming host is installed](/docs/troubleshooting#another-streaming-host-sunshine-apollo--is-installed).
+
 ## Environment
 
 Most behaviour (compositor, video source, input backend, zero-copy) is set in