feat: clearer Arguments editor with typed-together detection and one-click fix

- Label now explains the model with an example: a flag and its value go
  on separate lines. Placeholder shows the common uv pattern.
- split_suspicious_args() flags lines that contain whitespace plus a
  dash-prefixed token ('--directory /path') — legit single args with
  spaces ('My Documents') are never touched. Quotes are respected.
- The editor shows a warning under the args box with a 'Fix: split onto
  separate lines' button; the fix goes through the undo stack.

bcc_core.py

@@ -580,6 +580,42 @@ def parse_pasted_json(text: str) -> dict[str, dict]:
     return servers
 
 
+def split_suspicious_args(args: list[str]) -> tuple[list[str], list[str]]:
+    """
+    Detect the classic argument-entry mistake: several argv tokens typed on one
+    line ("--directory /path/to/server"). An entry is only flagged when it
+    contains whitespace AND at least one whitespace-separated token starts with
+    "-" — so legitimate single arguments with spaces ("My Project Notes",
+    "/Users/me/My Documents") are never touched.
+
+    Returns (fixed_args, notes). notes is empty when nothing was suspicious;
+    otherwise it describes each split so a UI can show the proposed fix.
+    Quotes are respected when splitting ('--name "My Server"' becomes
+    ['--name', 'My Server']).
+    """
+    import shlex
+
+    out: list[str] = []
+    notes: list[str] = []
+    for a in args:
+        if isinstance(a, str) and _looks_like_multiple_args(a):
+            try:
+                parts = shlex.split(a)
+            except ValueError:  # unbalanced quotes — fall back to plain split
+                parts = a.split()
+            if len(parts) > 1:
+                out.extend(parts)
+                notes.append(f"“{a}” looks like {len(parts)} arguments — split onto separate lines")
+                continue
+        out.append(a)
+    return out, notes
+
+
+def _looks_like_multiple_args(a: str) -> bool:
+    toks = a.split()
+    return len(toks) > 1 and any(t.startswith("-") for t in toks)
+
+
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 # Validation
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