fix(llm): honor model metadata cancellation and defaults

packages/ui/tui/tests/snapshots/model-effort-switching.expected.txt

@@ -26,9 +26,9 @@ buffer
   style 8-8 fg=bright-blue
   style 38-77 fg=bright-black
   style 83-83 fg=bright-blue
-15| "        │ → deepseek/deepseek-v4-pro        DeepSeek V4 Pro — Off                  │        "
+15| "        │ → deepseek/deepseek-v4-pro        DeepSeek V4 Pro — provider default     │        "
   style 8-8 fg=bright-blue
-  style 10-64 fg=bright-blue inverse
+  style 10-77 fg=bright-blue inverse
   style 83-83 fg=bright-blue
 16| "        │                                                                          │        "
   style 8-8 fg=bright-blue

packages/ui/tui/tests/snapshots/model-selector.expected.txt

@@ -26,9 +26,9 @@ buffer
   style 8-8 fg=bright-blue
   style 10-77 fg=bright-blue inverse
   style 83-83 fg=bright-blue
-15| "        │   deepseek/deepseek-v4-pro        DeepSeek V4 Pro — High                 │        "
+15| "        │   deepseek/deepseek-v4-pro        DeepSeek V4 Pro — provider default     │        "
   style 8-8 fg=bright-blue
-  style 36-65 fg=bright-black
+  style 36-77 fg=bright-black
   style 83-83 fg=bright-blue
 16| "        │                                                                          │        "
   style 8-8 fg=bright-blue

packages/ui/tui/tests/snapshots/model-switching.expected.txt

@@ -1,25 +1,27 @@
 terminal 92x32 buffer=normal length=32 base=0 viewport=0
 lifecycle started=1 stopped=0 progress=inactive
 title "DSH snapshot"
-cursor hidden column=1 viewportRow=6 bufferRow=6
+cursor hidden column=1 viewportRow=7 bufferRow=7
 buffer
 0| " DEEPSEEK HARNESS"
   style 1-8 fg=bright-blue bold
   style 10-16 bold
 1| " Snapshot agent ready."
   style 1-21 fg=bright-black
-2| " deepseek-v4-pro off  •  main-session"
-  style 1-36 dim
+2| " deepseek-v4-pro  •  main-session"
+  style 1-32 dim
 3| <blank>
-4| " Model selected: deepseek/deepseek-v4-pro. Reasoning effort: Off. New steps will use it.    "
-  style 1-87 fg=bright-black
-5| "────────────────────────────────────────────────────────────────────────────────────────────"
+4| " Model selected: deepseek/deepseek-v4-pro. Reasoning effort: provider default. New steps    "
+  style 1-91 fg=bright-black
+5| " will use it.                                                                               "
+  style 1-12 fg=bright-black
+6| "────────────────────────────────────────────────────────────────────────────────────────────"
   style 0-91 dim
-6| "                                                                                            "
+7| "                                                                                            "
   style 1-1 inverse
-7| "────────────────────────────────────────────────────────────────────────────────────────────"
+8| "────────────────────────────────────────────────────────────────────────────────────────────"
   style 0-91 dim
-8| "deepseek-v4-pro off  /workspace/project  ↑0 ↓0                   0% context  tools:collapsed"
-  style 0-45 dim
+9| "deepseek-v4-pro  /workspace/project  ↑0 ↓0                       0% context  tools:collapsed"
+  style 0-41 dim
   style 65-91 dim
-9-31| <blank>
+10-31| <blank>