feat(markdown): prefer tool description in callout title

src/beaver_gateway/frontends/markdown/renderer.py

@@ -42,9 +42,11 @@ USER_SCAFFOLD = "### User:\n"
 # contain ``` and we get language syntax highlighting in Obsidian for free.
 FENCE = "````"
 
-# Used when a tool input mentions a path/file we can dangle in the
-# callout title — purely cosmetic.
-_PATH_KEYS = ("path", "file", "filename", "url", "command", "query")
+# Input keys we dangle after the tool name in the callout title, best
+# first — purely cosmetic. ``description`` wins because when a tool
+# offers one it's a human-written summary of the call, which beats a
+# truncated shell command or path.
+_TITLE_KEYS = ("description", "path", "file", "filename", "url", "command", "query")
 
 
 def render_user_text(content: str) -> str:
@@ -114,9 +116,9 @@ def append_to_body(existing: str, new_block: str) -> str:
 def summarize_tool_input(name: str, tool_input: object) -> str:
     """Build the ``[!tool]- <summary>`` title string.
 
-    Tries to pick a single salient field (``path``, ``command``, etc.)
-    from the input dict so the collapsed callout shows something
-    meaningful in Obsidian. Falls back to just the tool name.
+    Tries to pick a single salient field (``description``, ``path``,
+    ``command``, etc.) from the input dict so the collapsed callout shows
+    something meaningful in Obsidian. Falls back to just the tool name.
     """
     if not isinstance(tool_input, dict):
         return name
@@ -125,7 +127,7 @@ def summarize_tool_input(name: str, tool_input: object) -> str:
     # cast keeps the rest of the function readable without sprinkling
     # per-line type narrowing on every ``.get`` call.
     d = cast("dict[str, Any]", tool_input)
-    for key in _PATH_KEYS:
+    for key in _TITLE_KEYS:
         value = d.get(key)
         if isinstance(value, str) and value:
             short = value if len(value) <= 60 else value[:57] + "..."