feat: add_visual_selection_inline should support non-file buffer (#442)

```
opts.keymap.output_window = {
  ['r'] = { 'add_visual_selection_inline', mode = { 'v' } },
}
```

Author: phanen

lua/opencode/context.lua

@@ -181,25 +181,28 @@ end
 function M.build_inline_selection_text(range)
   local buf = vim.api.nvim_get_current_buf()
 
-  if not util.is_buf_a_file(buf) then
-    vim.notify('Cannot add selection: not a file buffer', vim.log.levels.WARN)
-    return nil
-  end
-
   local current_selection = BaseContext.get_current_selection(nil, range)
   if not current_selection then
     vim.notify('No visual selection found', vim.log.levels.WARN)
     return nil
   end
 
   local file = BaseContext.get_current_file_for_selection(buf)
-  if not file then
-    vim.notify('Cannot determine file for selection', vim.log.levels.WARN)
-    return nil
-  end
 
+  local n = 3
+  current_selection.text:gsub('(`+)', function(run)
+    n = math.max(n, #run + 1)
+  end)
+
+  local fence = string.rep('`', n)
   local filetype = vim.bo[buf].filetype or ''
-  local text = string.format('**`%s`**\n\n```%s\n%s\n```', file.path, filetype, current_selection.text)
+  local code = current_selection.text:gsub('^%s+', ''):gsub('%s+$', '')
+  local text ---@type string
+  if file then
+    text = string.format('**`%s`**\n\n%s%s\n%s\n%s', file.path, fence, filetype, code, fence)
+  else
+    text = string.format('%s%s\n%s\n%s', fence, filetype, code, fence)
+  end
 
   return text
 end

tests/unit/context_spec.lua

@@ -1194,33 +1194,45 @@ describe('build_inline_selection_text', function()
     vim.bo = original_bo
   end)
 
-  it('should return nil and notify when not a file buffer', function()
+  it('should return formatted text without file path for non-file buffer', function()
     local original_is_buf_a_file = util.is_buf_a_file
+    local original_get_current_selection = BaseContext.get_current_selection
+    local original_get_current_file_for_selection = BaseContext.get_current_file_for_selection
     local original_get_current_buf = vim.api.nvim_get_current_buf
 
     util.is_buf_a_file = function()
       return false
     end
+    BaseContext.get_current_selection = function()
+      return { text = 'function foo()\n  return 42\nend', lines = '10, 12' }
+    end
+    BaseContext.get_current_file_for_selection = function()
+      return nil
+    end
     vim.api.nvim_get_current_buf = function()
       return 10
     end
 
-    local original_notify = vim.notify
-    local notifications = {}
-    vim.notify = function(msg, level)
-      table.insert(notifications, { msg = msg, level = level })
-    end
+    local original_bo = vim.bo
+    vim.bo = setmetatable({}, {
+      __index = function(_, _)
+        return { filetype = 'lua' }
+      end,
+    })
 
     local text = context.build_inline_selection_text()
 
-    assert.is_nil(text)
-    assert.equal(1, #notifications)
-    assert.equal('Cannot add selection: not a file buffer', notifications[1].msg)
-    assert.equal(vim.log.levels.WARN, notifications[1].level)
+    assert.is_not_nil(text)
+    assert.is_nil(text:match('%*%*`'))
+    assert.is_not_nil(text:match('```lua'))
+    assert.is_not_nil(text:match('function foo%(%)'))
+    assert.is_not_nil(text:match('```$'))
 
     util.is_buf_a_file = original_is_buf_a_file
+    BaseContext.get_current_selection = original_get_current_selection
+    BaseContext.get_current_file_for_selection = original_get_current_file_for_selection
     vim.api.nvim_get_current_buf = original_get_current_buf
-    vim.notify = original_notify
+    vim.bo = original_bo
   end)
 
   it('should return nil and notify when no visual selection found', function()