feat(supermaven): add on-demand autocompletion

Removes inline text suggestion and binds <C-t> to autocomplete. Under
the hood it activates inline text suggestion, accept the suggestion and
then disable it again. It removes the noise of AI text suggestions
while allowing me to take advantage of it when it's useful.

lua/custom/plugins/supermaven.lua

@@ -1,10 +1,6 @@
 return {
 	"supermaven-inc/supermaven-nvim",
-	opts = {
-		keymaps = {
-			accept_suggestion = "<C-y>",
-			clear_suggestion = "<C-]>",
-			accept_word = "<C-j>",
-		},
-	},
+	config = function()
+		require("custom.supermaven")
+	end
 }

lua/custom/supermaven.lua

@@ -0,0 +1,24 @@
+require("supermaven-nvim").setup({
+	disable_keymaps = true,
+	disable_inline_completion = true,
+	log_level = "info",
+})
+
+-- Supermaven on-demand configuration
+local suggestion = require('supermaven-nvim.completion_preview')
+
+local function on_demand_complete()
+	vim.g.supermaven_inline_completion_enabled = true
+
+	vim.schedule(function()
+		if suggestion.has_suggestion() then
+			suggestion.on_accept_suggestion()
+		end
+
+		vim.g.supermaven_inline_completion_enabled = false
+	end)
+
+	return ""
+end
+
+vim.keymap.set('i', '<C-t>', on_demand_complete, { expr = true, silent = true, desc = "On-demand Supermaven completion" })