feat(display): edid_lock policy axis — pin AMD connector EDID emulation while streaming

Productizes the adl-emul probe (the prior commit) as the display-policy axis its
PR promised: the ADL FFI moves to pf_win_display::adl_emul (one surface shared by
the probe tool and the host, so a reporter's probe and the console's toggle
exercise byte-identical driver calls), and an EXPERIMENTAL edid_lock axis joins
ddc_power_off/pnp_disable_monitors — orthogonal to presets, off by default.

At the first Exclusive isolate the host pins each occupied AMD connector's live
EDID + ADL_EMUL_MODE_ALWAYS (the software HPD dummy) BEFORE the physicals
deactivate; last-member teardown unlocks. Pinned emulation outlives the process,
so a crash journal (edid-lock-active.json) unlocks on the next host start,
mirroring the pnp_disable_monitors recovery. Inert without an AMD driver.

The console shows the toggle ONLY when the GPU inventory lists an AMD adapter —
the lever exists nowhere else, and a toggle that can never act is the 'saved and
then did nothing' trap the enforced-axes list exists to prevent.

api/openapi.json

@@ -4753,6 +4753,10 @@
             "type": "boolean",
             "description": "EXPERIMENTAL (Windows): command physical monitors' panels off over DDC/CI (VCP 0xD6 →\nDPMS off) right before an `Exclusive` isolate deactivates them, and back on at restore.\nTargets the \"connected-but-dark head\" periodic-stutter class (monitor standby\nauto-input-scan / DP link churn while the virtual display is the sole active display) at\nthe monitor-firmware level. Best-effort — monitors without DDC/CI (or with it disabled in\nthe OSD) are skipped. Orthogonal to `preset` (like `game_session`): preserved across\npreset changes; `#[serde(default)]` = off so existing `display-settings.json` files are\nuntouched."
           },
+          "edid_lock": {
+            "type": "boolean",
+            "description": "**EXPERIMENTAL, AMD-only in effect: pin connector EDID emulation while streaming** — the\nsoftware equivalent of an HPD-holding dummy plug (`pf_win_display::adl_emul`). Locked at\nthe first Exclusive isolate BEFORE the physicals deactivate (an awake sink answers its\nlive-EDID read), unlocked at last-member teardown, crash-journaled so a dead host unlocks\non its next start. Targets the standby-sink stall class at its SOURCE: with emulation\npinned the KMD stops servicing the sleeping sink's HPD/DDC/link. Inert without an AMD\ndriver (`atiadlxx.dll` absent) and on non-Windows. Orthogonal to `preset` (like\n`game_session`); `#[serde(default)]` = off."
+          },
           "game_session": {
             "$ref": "#/components/schemas/GameSession",
             "description": "How a game-launching session is served (`design/gamemode-and-dedicated-sessions.md` §5.2).\nOrthogonal to `preset`/lifecycle — preserved across preset changes; `#[serde(default)]` = `Auto`\nso existing `display-settings.json` files are untouched."