fix(submit): use file path over stdin; fix CF CodeMirror textarea (#305)

## Problem

After the initial submit hardening, two issues remained: source code was
read in Lua and piped as stdin to the scraper (unnecessary roundtrip
since
the file exists on disk), and CF's `page.fill()` timed out on the hidden
`textarea[name="source"]` because CodeMirror owns the editor state.

## Solution

Pass the source file path as a CLI arg instead — AtCoder calls
`page.set_input_files(file_path)` directly, CF reads it with
`Path(file_path).read_text()`. Fix CF source injection via
`page.evaluate()`
into the CodeMirror instance. Extract `BROWSER_SUBMIT_NAV_TIMEOUT` as a
per-platform `defaultdict` (CF defaults to 2× nav timeout). Save the
buffer
with `vim.cmd.update()` before submitting.

lua/cp/submit.lua

@@ -19,7 +19,7 @@ local function prompt_credentials(platform, callback)
   end
   vim.ui.input({ prompt = platform .. ' username: ' }, function(username)
     if not username or username == '' then
-      logger.log('Submit cancelled', vim.log.levels.WARN)
+      logger.log('Submit cancelled', { level = vim.log.levels.WARN })
       return
     end
     vim.fn.inputsave()
@@ -27,7 +27,7 @@ local function prompt_credentials(platform, callback)
     vim.fn.inputrestore()
     vim.cmd.redraw()
     if not password or password == '' then
-      logger.log('Submit cancelled', vim.log.levels.WARN)
+      logger.log('Submit cancelled', { level = vim.log.levels.WARN })
       return
     end
     local creds = { username = username, password = password }
@@ -42,20 +42,21 @@ function M.submit(opts)
   local problem_id = state.get_problem_id()
   local language = (opts and opts.language) or state.get_language()
   if not platform or not contest_id or not problem_id or not language then
-    logger.log('No active problem. Use :CP <platform> <contest> first.', vim.log.levels.ERROR)
+    logger.log(
+      'No active problem. Use :CP <platform> <contest> first.',
+      { level = vim.log.levels.ERROR }
+    )
     return
   end
 
   local source_file = state.get_source_file()
   if not source_file or vim.fn.filereadable(source_file) ~= 1 then
-    logger.log('Source file not found', vim.log.levels.ERROR)
+    logger.log('Source file not found', { level = vim.log.levels.ERROR })
     return
   end
 
   prompt_credentials(platform, function(creds)
-    local source_lines = vim.fn.readfile(source_file)
-    local source_code = table.concat(source_lines, '\n')
-
+    vim.cmd.update()
     vim.notify('[cp.nvim] Submitting...', vim.log.levels.INFO)
 
     require('cp.scraper').submit(
@@ -63,7 +64,7 @@ function M.submit(opts)
       contest_id,
       problem_id,
       language,
-      source_code,
+      source_file,
       creds,
       function(ev)
         vim.schedule(function()
@@ -73,12 +74,13 @@ function M.submit(opts)
       function(result)
         vim.schedule(function()
           if result and result.success then
-            logger.log('Submitted successfully', vim.log.levels.INFO, true)
+            logger.log('Submitted successfully', { level = vim.log.levels.INFO, override = true })
           else
-            logger.log(
-              'Submit failed: ' .. (result and result.error or 'unknown error'),
-              vim.log.levels.ERROR
-            )
+            local err = result and result.error or 'unknown error'
+            if err:match('^Login failed') then
+              cache.clear_credentials(platform)
+            end
+            logger.log('Submit failed: ' .. err, { level = vim.log.levels.ERROR })
           end
         end)
       end