agent_ui: Remove context strip from inline assistant (#42633)

TODO
- [x] Implement PromptEditor::paste
- [x] Fix creases on unlink
- [x] PromptCompletionProviderDelegate::supports_images
- [ ] Fix highlighting in completion menu

Release Notes:

- N/A

---------

Co-authored-by: Danilo Leal <daniloleal09@gmail.com>

assets/keymaps/default-linux.json

@@ -239,13 +239,11 @@
       "ctrl-alt-l": "agent::OpenRulesLibrary",
       "ctrl-i": "agent::ToggleProfileSelector",
       "ctrl-alt-/": "agent::ToggleModelSelector",
-      "ctrl-shift-a": "agent::ToggleContextPicker",
       "ctrl-shift-j": "agent::ToggleNavigationMenu",
       "ctrl-alt-i": "agent::ToggleOptionsMenu",
       "ctrl-alt-shift-n": "agent::ToggleNewThreadMenu",
       "shift-alt-escape": "agent::ExpandMessageEditor",
       "ctrl->": "agent::AddSelectionToThread",
-      "ctrl-alt-e": "agent::RemoveAllContext",
       "ctrl-shift-e": "project_panel::ToggleFocus",
       "ctrl-shift-enter": "agent::ContinueThread",
       "super-ctrl-b": "agent::ToggleBurnMode",
@@ -322,17 +320,6 @@
       "alt-enter": "editor::Newline"
     }
   },
-  {
-    "context": "ContextStrip",
-    "bindings": {
-      "up": "agent::FocusUp",
-      "right": "agent::FocusRight",
-      "left": "agent::FocusLeft",
-      "down": "agent::FocusDown",
-      "backspace": "agent::RemoveFocusedContext",
-      "enter": "agent::AcceptSuggestedContext"
-    }
-  },
   {
     "context": "AcpThread > ModeSelector",
     "bindings": {
@@ -824,8 +811,7 @@
     "context": "PromptEditor",
     "bindings": {
       "ctrl-[": "agent::CyclePreviousInlineAssist",
-      "ctrl-]": "agent::CycleNextInlineAssist",
-      "ctrl-alt-e": "agent::RemoveAllContext"
+      "ctrl-]": "agent::CycleNextInlineAssist"
     }
   },
   {