feat(picker): open contest picker directly from :CP <platform>

Problem: `:CP codechef` (platform with no contest) returned a "too few
arguments" error, forcing users to type `:CP pick` separately.

Solution: When a platform name is given with no contest, parse it as a
`pick` action with the platform pre-selected, skipping the platform
selection step in the picker UI.

lua/cp/commands/init.lua

@@ -257,10 +257,7 @@ local function parse_command(args)
 
   if vim.tbl_contains(platforms, first) then
     if #args == 1 then
-      return {
-        type = 'error',
-        message = 'Too few arguments - specify a contest.',
-      }
+      return { type = 'action', action = 'pick', requires_context = false, platform = first }
     elseif #args == 2 then
       if args[2] == 'login' or args[2] == 'logout' or args[2] == 'signup' then
         return { type = 'action', action = args[2], requires_context = false, platform = first }
@@ -362,6 +359,7 @@ local function check_platform_enabled(platform)
 end
 
 --- Core logic for handling `:CP ...` commands
+---@param opts { fargs: string[] }
 ---@return nil
 function M.handle_command(opts)
   local cmd = parse_command(opts.fargs)
@@ -400,7 +398,7 @@ function M.handle_command(opts)
       setup.navigate_problem(-1, cmd.language)
     elseif cmd.action == 'pick' then
       local picker = require('cp.commands.picker')
-      picker.handle_pick_action(cmd.language)
+      picker.handle_pick_action(cmd.language, cmd.platform)
     elseif cmd.action == 'edit' then
       local edit = require('cp.ui.edit')
       edit.toggle_edit(cmd.test_index)

lua/cp/commands/picker.lua

@@ -5,8 +5,9 @@ local logger = require('cp.log')
 
 --- Dispatch `:CP pick` to appropriate picker
 ---@param language? string
+---@param platform? string
 ---@return nil
-function M.handle_pick_action(language)
+function M.handle_pick_action(language, platform)
   local config = config_module.get_config()
 
   if not (config.ui and config.ui.picker) then
@@ -54,7 +55,7 @@ function M.handle_pick_action(language)
     picker = fzf_picker
   end
 
-  picker.pick(language)
+  picker.pick(language, platform)
 end
 
 return M

lua/cp/pickers/fzf_lua.lua

@@ -58,11 +58,18 @@ local function contest_picker(platform, refresh, language)
   })
 end
 
-function M.pick(language)
+---@param language? string
+---@param platform? string
+function M.pick(language, platform)
+  if platform then
+    contest_picker(platform, false, language)
+    return
+  end
+
   local fzf = require('fzf-lua')
   local platforms = picker_utils.get_platforms()
-  local entries = vim.tbl_map(function(platform)
-    return platform.display_name
+  local entries = vim.tbl_map(function(p)
+    return p.display_name
   end, platforms)
 
   return fzf.fzf_exec(entries, {
@@ -74,16 +81,16 @@ function M.pick(language)
         end
 
         local selected_name = selected[1]
-        local platform = nil
+        local found = nil
         for _, p in ipairs(platforms) do
           if p.display_name == selected_name then
-            platform = p
+            found = p
             break
           end
         end
 
-        if platform then
-          contest_picker(platform.id, false, language)
+        if found then
+          contest_picker(found.id, false, language)
         end
       end,
     },

lua/cp/pickers/telescope.lua

@@ -64,7 +64,14 @@ local function contest_picker(opts, platform, refresh, language)
     :find()
 end
 
-function M.pick(language)
+---@param language? string
+---@param platform? string
+function M.pick(language, platform)
+  if platform then
+    contest_picker({}, platform, false, language)
+    return
+  end
+
   local opts = {}
   local platforms = picker_utils.get_platforms()