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>

README.md

@@ -29,6 +29,11 @@ protocol, FEC, and crypto, linked into the host and every client over a stable C
 - **Your device's exact mode.** For each client that connects, the host spins up a virtual display
   sized to that device — 1080p60 to a laptop, 1440p120 to a desktop, 4K to a TV, all at once. No
   letterboxing, no scaling, no rearranging your real monitors.
+- **Displays you configure, not just create.** Keep a game's display (and the game) alive across
+  disconnects so a reconnect drops straight back in; make the stream your sole desktop or extend
+  alongside your monitors; let several devices become monitors of one desktop; keep each client's
+  scaling. One-click presets in the console — a dedicated couch box, a shared desktop, a multi-monitor
+  workstation. See [Virtual displays](docs-site/content/docs/virtual-displays.md).
 - **A real virtual display on Windows, too.** On Linux the host uses per-compositor virtual outputs;
   on Windows you get the same on-the-fly virtual display — at the client's exact mode, no physical
   monitor or dummy HDMI plug, even on the secure desktop (UAC / lock screen). It also has **its own