fix(exec): refine format command deny pattern to allow URL parameters

The previous regex r"(?:^|[;&|]\s*)format\b" incorrectly blocked
commands containing URL parameters like &format=json. Added negative
lookahead (?!=) so format= (URL param key=value) is allowed while
standalone format commands (e.g. ;format, &format, |format) remain
blocked. Added test cases for both blocking and allowing scenarios.

nanobot/agent/tools/shell.py

@@ -106,7 +106,7 @@ class ExecTool(Tool):
             r"\brm\s+-[rf]{1,2}\b",          # rm -r, rm -rf, rm -fr
             r"\bdel\s+/[fq]\b",              # del /f, del /q
             r"\brmdir\s+/s\b",               # rmdir /s
-            r"(?:^|[;&|]\s*)format\b",       # format (as standalone command only)
+            r"(?:^|[;&|]\s*)format(?!=)\b",   # format (as standalone command only)
             r"\b(mkfs|diskpart)\b",          # disk operations
             r"\bdd\s+if=",                   # dd
             r">\s*/dev/sd",                  # write to disk