Drop named-unit frames and the pfValidUnits global

CreateUnitFrame and CreateCastbar could take a character name instead of
a unit token, but every caller passes a token, so that mode and the
empty-label guards around it were dead. The OnClick TargetByName branch
could never run anyway: label was always a string, and "" is truthy.

With that gone, the aggro scan was the only reader of pfValidUnits, so
its unit list now lives in unitframes.lua and is built once at load.

/focusname resolves the name with UnitTokenFromName (exact first, then
prefix) instead of swapping the target and muting UIErrorsFrame.

env/tables.lua

@@ -13,38 +13,3 @@ pfGridmath = {
   [11] = {{11,1},{1,11}},
   [12] = {{12,1},{6,2},{4,3},{3,4},{2,6},{1,12}}
 }
-
--- list of valid unitstrings
-pfValidUnits = {}
-pfValidUnits["pet"] = true
-pfValidUnits["player"] = true
-pfValidUnits["target"] = true
-pfValidUnits["mouseover"] = true
-
-pfValidUnits["focus"] = true
-pfValidUnits["focustarget"] = true
-pfValidUnits["focustargettarget"] = true
-
-pfValidUnits["pettarget"] = true
-pfValidUnits["playertarget"] = true
-pfValidUnits["targettarget"] = true
-pfValidUnits["mouseovertarget"] = true
-pfValidUnits["targettargettarget"] = true
-
-for i=1,4 do
-  pfValidUnits["party" .. i] = true
-  pfValidUnits["party" .. i .. "target"] = true
-  pfValidUnits["partypet" .. i] = true
-  pfValidUnits["partypet" .. i .. "target"] = true
-end
-
-for i=1,40 do
-  pfValidUnits["raid" .. i] = true
-  pfValidUnits["raid" .. i .. "target"] = true
-
-  pfValidUnits["raidpet" .. i] = true
-  pfValidUnits["raidpet" .. i .. "target"] = true
-
-  pfValidUnits["nameplate" .. i] = true
-  pfValidUnits["nameplate" .. i .. "target"] = true
-end