feat(notifications): add overlay notifications with position config

- Add Catppuccin Macchiato overlay notification stack with 3s transient timeout
- Add `notifications.overlayPosition` config (top-left | top | top-right)
- Route startup tokenization and subtitle annotation status through configured surfaces
- Deduplicate rapid subtitle mode toggle notifications
- Change `both` to mean overlay + system; add `osd-system` as legacy alias for old behavior
- Keep `osd`/`osd-system` as config-file-only legacy values; Settings UI offers overlay/system/both/none

plugin/subminer/messages.lua

@@ -2,6 +2,7 @@ local M = {}
 
 function M.create(ctx)
 	local mp = ctx.mp
+	local opts = ctx.opts
 	local process = ctx.process
 	local hover = ctx.hover
 	local ui = ctx.ui
@@ -49,7 +50,9 @@ function M.create(ctx)
 			hover.handle_hover_message(payload_json)
 		end)
 		mp.register_script_message("subminer-stats-toggle", function()
-			mp.osd_message("Stats: press ` (backtick) in overlay", 3)
+			if opts.osd_messages then
+				mp.osd_message("Stats: press ` (backtick) in overlay", 3)
+			end
 		end)
 		mp.register_script_message("subminer-reload-session-bindings", function()
 			ctx.session_bindings.reload_bindings()