docs(display-management): Stage 8 consolidation — docs page, README, CLAUDE.md, host.env

Bring the user-facing + project docs in line with the shipped, on-glass-validated state (Stages
0-5 §6A + keep-alive hardening + gaming-rig) ahead of a merge decision:

- docs-site/virtual-displays.md: drop the now-false "stored but not yet enforced / following
  release" caveats — conflict handling, per-client identity + KDE scaling round-trip, and §6A
  multi-monitor layout are all live; gaming-rig/forever ships (freed via Release); document the
  reconnect-always-resumes + deliberate-quit-skips-linger behavior and the PUNKTFUNK_IDLE_TIMEOUT_MS
  knob. KDE persistent scaling → ✅ today (validated); Windows primary → shipped; Sway exclusive
  stays "following release".
- README: a "displays you configure, not just create" differentiator bullet.
- CLAUDE.md: the display-management invariant now reflects Stages 0-5 shipped (all axes enforced,
  forever/Pinned, hardened reconnect) instead of "Stage 0 shipped".
- host.env.example: document PUNKTFUNK_IDLE_TIMEOUT_MS + that display policy lives in the console.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

scripts/host.env.example

@@ -48,6 +48,15 @@ PUNKTFUNK_ZEROCOPY=1
 #PUNKTFUNK_INPUT_BACKEND=libei      # wlr | libei | gamescope | uinput
 #PUNKTFUNK_FEC_PCT=20               # video FEC overhead percent
 #PUNKTFUNK_PERF=1                   # per-stage timing logs
+# Display-management policy (keep-alive · topology · conflict · identity · layout · max) is set in the
+# web console (Host → Virtual displays) → ~/.config/punktfunk/display-settings.json, NOT here; a
+# settings file supersedes the legacy PUNKTFUNK_MONITOR_LINGER_MS / _NO_ISOLATE / *_VIRTUAL_PRIMARY
+# knobs. One transport knob has no console equivalent:
+#PUNKTFUNK_IDLE_TIMEOUT_MS=8000     # disconnect-detection latency: how long before a DROPPED client is
+                                    # declared gone (a kept display then starts its linger, or frees).
+                                    # Lower (e.g. 3000) to reclaim kept displays sooner after an
+                                    # ungraceful drop; clamped ≥1s, keep-alive ping scales with it so a
+                                    # live session never false-disconnects. A deliberate quit is instant.
 # Full-chroma 4:4:4 (HEVC Range Extensions) — sharper text/desktop, no chroma loss. Honored only on
 # the punktfunk/1 native path when the client advertises 4:4:4 AND the GPU supports it (probed; else
 # the session stays 4:2:0). HEVC-only; independent of 10-bit. NVENC (NVIDIA) is the validated path;