Need built-in envelope unwrap for `claude --print --output-format json` responses

[ameet]

Description

When flows call `claude --print --output-format json` via bash steps, the response is wrapped in an envelope:

{"type": "result", "result": "```json\n{\"actual\": \"data\"}\n```"}

Every flow that consumes this output must implement identical unwrap logic:

1. Detect the `{"type": "result", "result": "..."}` envelope
2. Strip markdown fences (```json ... ```)
3. Strip any preamble text before the JSON
4. Parse the inner JSON
5. Handle parse failures gracefully

This pattern is duplicated 20+ times across flows. Each copy is ~8 lines of JavaScript.

Current Workaround

Each code step defines an inline `unwrap()` function:

var unwrap = function(r) {
  if (r && r.type === 'result' && r.result) {
    var s = String(r.result)
      .replace(/^\`\`\`[a-z]*\\s*\\n?/gm, '')
      .replace(/\\n?\`\`\`\\s*$/gm, '')
      .trim();
    try { return JSON.parse(s); } catch(e) { return r; }
  }
  return r;
};
raw = unwrap(raw);

Suggested Fix

One or more of:

1. `parseEnvelope: true` option on bash steps — automatically unwrap the Claude envelope before passing to downstream steps
2. Built-in helper exposed to code steps — e.g., `$.unwrapEnvelope(raw)` available in the sandbox
3. `--raw-json` flag for `claude --print` — return just the JSON without the envelope (this may be an Anthropic CLI issue, not One CLI)

[siddharth-bhansali]

Implemented in #168 — parseEnvelope: true on bash steps unwraps the claude --print envelope (.result → fence strip → preamble removal → parse inner JSON), failing the step on invalid JSON. Replaces the per-flow unwrap() helpers. Will close on merge.