Rebuild Displays around the canvas, and let the transaction keep color

Claude-Session: https://claude.ai/code/session_01Ms2FbjQy31TVf3CEvQhGM8

tests/quickshell/displays-contract

@@ -48,6 +48,15 @@ for contract in \
     'primary: monitor.name === primaryName'; do
     rg -Fq "$contract" "$service" || fail "display service contract is missing: $contract"
 done
+# The rest of the record rides the same transaction. Colour and mirroring are
+# verified by readback like geometry; the VRR override is applied and never
+# verified, because the readback field is live adaptive-sync state rather than
+# the configured policy. Either way they are part of currentLayout, which is
+# what stops one apply from clobbering another field's value.
+for contract in 'colorProfile' 'bitdepth' 'sdrBrightness' 'mirrorOf' 'vrrMode'; do
+    rg -Fq "$contract" "$service" || fail "the extended display record is missing: $contract"
+done
+
 rg -Fq 'enabled: Displays.canConfirm' "$page" \
     || fail 'Keep is enabled before the display change is verified'
 rg -Fq 'options: Displays.scalesForMode(' "$page" \
@@ -67,7 +76,8 @@ rg -Fq 'if (root.busy)' "$service" \
 
 # Stored JSON is untyped at field level, so the Lua startup consumer is the
 # final validation boundary and must support every named output it accepts.
-for contract in 'valid_mode' 'valid_scale' 'valid_transform' 'valid_position' 'valid_primary' 'pairs(displays)'; do
+for contract in 'valid_mode' 'valid_scale' 'valid_transform' 'valid_position' 'valid_primary' \
+    'color_profile' 'bitdepth_value' 'vrr_value' 'sdr_value' 'mirror_value' 'pairs(displays)'; do
     rg -Fq "$contract" "$monitors_lua" || fail "monitor startup validation is missing: $contract"
 done
 
@@ -93,6 +103,7 @@ package.preload["prefs"] = function()
                 ["HDMI-A-1"] = {
                     mode = "2560x1440@60", scale = 1, transform = 1,
                     x = 3000, y = 0, primary = false,
+                    vrrMode = -1,
                 },
                 ["LEGACY-1"] = { mode = "1920x1080@60", scale = 1.5, transform = 0 },
                 ["PARTIAL-1"] = {
@@ -107,6 +118,24 @@ package.preload["prefs"] = function()
                     mode = "1920x1080@60", scale = 1, transform = 0,
                     x = 4440, y = 0, primary = false,
                 },
+                -- The extended record, as Settings stores it.
+                ["DP-3"] = {
+                    mode = "1920x1080@60", scale = 1, transform = 0,
+                    x = 4440, y = 0, primary = false,
+                    colorProfile = "srgb", bitdepth = 10,
+                    sdrBrightness = 1.2, sdrSaturation = 1.0,
+                    vrrMode = 2, mirrorOf = "DP-2",
+                },
+                -- Every new field impossible at once. Geometry is fine, so the
+                -- display is still configured; the bad fields drop out one by
+                -- one exactly as an invalid position does.
+                ["DP-4"] = {
+                    mode = "1920x1080@60", scale = 1, transform = 0,
+                    x = 6360, y = 0, primary = false,
+                    colorProfile = "neon", bitdepth = 12,
+                    sdrBrightness = 9, sdrSaturation = -1,
+                    vrrMode = 7, mirrorOf = "BAD OUTPUT",
+                },
             }
         end,
     }
@@ -139,9 +168,38 @@ assert(by_output["PARTIAL-1"] == nil)
 assert(by_output["BAD-PRIMARY"] == nil)
 assert(by_output["BAD OUTPUT"] == nil)
 assert(by_output[""] ~= nil)
+
+-- The extended record reaches the compositor under Hyprland's own key names.
+assert(by_output["DP-3"].cm == "srgb")
+assert(by_output["DP-3"].bitdepth == 10)
+assert(by_output["DP-3"].sdrbrightness == 1.2)
+assert(by_output["DP-3"].vrr == 2)
+assert(by_output["DP-3"].mirror == "DP-2")
+-- A mirrored output shows its target's picture in its target's place, so the
+-- saved position is not ours to ask for.
+assert(by_output["DP-3"].position == "auto")
+-- Neutral SDR saturation is left out rather than written: a rule that names it
+-- pins the display to it.
+assert(by_output["DP-3"].sdrsaturation == nil)
+
+-- -1 means "follow the global policy", which is the absence of an override,
+-- not an override with a special value. Writing a vrr key here would silently
+-- take this display out of the gaming policy it is meant to follow.
+assert(by_output["HDMI-A-1"].vrr == nil)
+
+-- Bad fields drop, the display survives. This is the same fallback invalid
+-- geometry gets, and it matters more here: refusing the whole entry over an
+-- unreadable colour profile would lose the resolution too.
+assert(by_output["DP-4"] ~= nil)
+assert(by_output["DP-4"].position == "6360x0")
+assert(by_output["DP-4"].cm == nil)
+assert(by_output["DP-4"].bitdepth == nil)
+assert(by_output["DP-4"].sdrbrightness == nil)
+assert(by_output["DP-4"].vrr == nil)
+assert(by_output["DP-4"].mirror == nil)
 LUA
 
-rg -Fq 'Resolution, scale, rotation, position, and primary display' \
+rg -Fq 'Resolution, scale, rotation, position, primary display, color, VRR override, and mirroring' \
     "$repo_dir/config/dot/quickshell/config/PreferenceSchema.qml" \
     || fail 'the display preference does not document complete layout persistence'