Uncaught error text in Slice.evalSandbox repeats the source location #45

The error text for an uncaught exception in Slice.evalSandbox repeats the source location on the stack frame line.

Repro (throw.js)

const r = Slice.evalSandbox('throw new Error("boom")');
console.log(r.error);

slice run throw.js

Expected

Uncaught Error: boom (unknown at :2:7)
    at <main> (unknown at :2:7)

Actual

Uncaught Error: boom (unknown at :2:7)
    at <main> (unknown at :2:7) (unknown at :2:7)

The same text is returned in the error field of slice mcp slice_eval_ts.

Minor, but this text is shown directly to users and agents, and the line number :2 for a one-line snippet suggests the reported position includes an internal wrapper line, which may also be worth correcting.

Environment

• Version: v0.10.6, commit c6b3e77
• OS: Windows 11 x64, release build (cargo build --release)