Implement Error.captureStackTrace

[frostney]

Summary

Implement the Stage 2 TC39 proposal: https://github.com/tc39/proposal-error-capturestacktrace

Add captureStackTrace(target[, constructorOpt]) with arbitrary-object mutation, frame elision, descriptors, and proposal errors.

Why

This proposal fits GocciaScript's modern ECMAScript surface and the 0.13.0 proposal roadmap. It should extend the engine's existing architecture rather than arrive as a userland shim.

Current behavior

Lazy Error stack data and Error.prototype.stack accessors exist, but Error.captureStackTrace is absent.

Expected behavior

Add captureStackTrace(target[, constructorOpt]) with arbitrary-object mutation, frame elision, descriptors, and proposal errors.

Scope notes

Reuse CallStack and existing formatting; do not add prepareStackTrace or structured frames. Cover Error/non-Error targets, proxies, non-extensible objects, existing stack properties, missing cutoffs, realms, bound/native functions, docs, and tests. Additive API: no flag.

Related bytecode roadmap: #871 and #875. Update the relevant language/built-in documentation and Goccia proposal inventory. Use the proposal repository and its current specification at implementation time; add focused project tests and matching pinned Test262/proposal coverage without regressions.

Acceptance criteria

• Parser/API surface, descriptors, evaluation order, errors, and observable protocol behavior match the current proposal.
• Implementation uses the identified shared engine seam without a duplicate compatibility shim.
• Focused positive, negative, abrupt-completion, and edge-case tests cover the proposal.
• Relevant project suites, pinned Test262 cases, formatting, and documentation checks pass.