Convert a PBT repro into a regression test (x07 fix --from-pbt)

When x07 test --pbt finds a counterexample, it writes a repro artifact (repro.json). x07 fix --from-pbt turns that artifact into a committable, deterministic regression test by:

1. writing a tiny wrapper module that decodes input case bytes and calls the original property, and
2. appending a new tests/tests.json entry that feeds the minimized input_b64.

This lets you reproduce the failure with plain x07 test (no fuzz loop).

Workflow

1. Run PBT to produce repro.json:

   x07 test --pbt --manifest tests/tests.json --keep-artifacts

2. Convert the repro into a regression test:

   x07 fix --from-pbt target/x07test/pbt/<...>/repro.json --write

3. Re-run unit tests (now includes the new deterministic repro test):

   x07 test --manifest tests/tests.json

Fix the bug, then x07 test should go green.

What gets written

Given a repro with counterexample.case_bytes_b64 decoded to case_bytes, x07 fix --from-pbt computes:

• case_tag = "c" + sha256(case_bytes)[0..12]

and writes:

• Wrapper module: tests/repro/pbt/<case_tag>.x07.json
  • module id: repro.pbt.<case_tag>
  • exported entry: repro.pbt.<case_tag>.run
• Copied repro (canonicalized): tests/repro/pbt/<case_tag>.repro.json
• Manifest entry appended to tests/tests.json:
  • id: pbt_repro/<orig_test_id>/<case_tag>
  • entry: repro.pbt.<case_tag>.run
  • returns: bytes_status_v1
  • expect: pass
  • input_b64: the repro’s counterexample.case_bytes_b64

If the wrapper/repro files already exist and are identical, x07 fix --from-pbt is a no-op. If they exist but differ, it fails (never overwrites silently).

Report output

x07 fix --from-pbt prints an x07c.report@0.1.0 JSON to stdout with an info diagnostic:

• code: X07-PBT-FIX-INFO-0001
• data: written paths + ids + case hash metadata

Supported parameter types (v0.1)

Wrapper generation currently supports:

• i32
• bytes