feat: v0.4.1 — ChatGPT tool-output content types and conv_id fix

First real-data export against v0.4.0 surfaced 66 unknown blocks across
three content types — captured live and added.

Added:
- execution_output (Code Interpreter / container.exec / python tool
  output) → tool_result block. output=content.text,
  tool_name=author.name, is_error=metadata.aggregate_result.status,
  summary=metadata.reasoning_title
- system_error → error tool_result with tool_name=author.name
- tether_browsing_display: spinner placeholders (empty result+summary)
  skip silently with DEBUG log; defensive populated-case branch maps
  to tool_result (untested in real data)
- tool_result block schema: optional `summary` field rendered as
  italic line between header and fence
- tool_result rendering: tool_name appears in header when present
  (e.g. `📤 Result: container.exec`); existing tool_name=None calls
  unchanged
- _ROLE_LABELS["tool"] = ("🔧 Tool", "tool")

Fixed:
- chatgpt.normalize_conversation reads `conversation_id` as fallback
  for `id`. Live API uses conversation_id; fixtures use id.
  Pre-fix: empty id in YAML frontmatter and missing context in
  WARNING logs.

Tests: 11 new (192 total, 0 failures). Fixture extended with 4
tool-output cases (execution_output success, empty execution_output
that should skip, system_error, tether_browsing_display spinner).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

tests/fixtures/chatgpt_conversation.json

@@ -112,7 +112,7 @@
     "node-image-only": {
       "id": "node-image-only",
       "parent": "node-mm-user-rev",
-      "children": [],
+      "children": ["node-exec-output"],
       "message": {
         "id": "node-image-only",
         "author": {"role": "user"},
@@ -124,6 +124,73 @@
           ]
         }
       }
+    },
+    "node-exec-output": {
+      "id": "node-exec-output",
+      "parent": "node-image-only",
+      "children": ["node-exec-output-empty"],
+      "message": {
+        "id": "node-exec-output",
+        "author": {"role": "tool", "name": "container.exec", "metadata": {}},
+        "create_time": 1704067600.0,
+        "content": {
+          "content_type": "execution_output",
+          "text": "Hello from container.exec\nLine 2 of output"
+        },
+        "metadata": {
+          "aggregate_result": {"status": "success", "messages": []},
+          "reasoning_title": "Reading skill documentation"
+        }
+      }
+    },
+    "node-exec-output-empty": {
+      "id": "node-exec-output-empty",
+      "parent": "node-exec-output",
+      "children": ["node-system-error"],
+      "message": {
+        "id": "node-exec-output-empty",
+        "author": {"role": "tool", "name": "python", "metadata": {}},
+        "create_time": 1704067610.0,
+        "content": {
+          "content_type": "execution_output",
+          "text": ""
+        },
+        "metadata": {}
+      }
+    },
+    "node-system-error": {
+      "id": "node-system-error",
+      "parent": "node-exec-output-empty",
+      "children": ["node-tether-spinner"],
+      "message": {
+        "id": "node-system-error",
+        "author": {"role": "tool", "name": "web", "metadata": {}},
+        "create_time": 1704067620.0,
+        "content": {
+          "content_type": "system_error",
+          "name": "tool_error",
+          "text": "Error: Error from browse service: Error calling browse service: 503"
+        },
+        "metadata": {}
+      }
+    },
+    "node-tether-spinner": {
+      "id": "node-tether-spinner",
+      "parent": "node-system-error",
+      "children": [],
+      "message": {
+        "id": "node-tether-spinner",
+        "author": {"role": "tool", "name": "file_search", "metadata": {}},
+        "create_time": 1704067630.0,
+        "content": {
+          "content_type": "tether_browsing_display",
+          "result": "",
+          "summary": "",
+          "assets": null,
+          "tether_id": null
+        },
+        "metadata": {"command": "spinner", "status": "running"}
+      }
     }
   }
 }