Extends #26573 to also catch the case the original PR deliberately left
out: when a tool raises an exception, the agent's tool executor wraps it
in a canonical 'Error executing tool '<name>': ...' string prefix (see
agent/tool_executor.py around the try/except). That prefix is unique to
the wrapper and cannot legitimately appear in well-behaved tool output,
so it is a safe signal that the tool blew up.
Without this, the canonical 'tool raised' case still rendered as a green
'completed' row in Zed despite being a runtime failure — exactly the
class of bug #26573 set out to fix.
Adds a positive test (raised-exception prefix -> failed) and a negative
test (bare 'Error:' word in legit tool output stays completed) so a
future contributor doesn't accidentally widen the rule to false-positive
on compiler/linter diagnostics.
eda1c97a1e