fix(reports): every report format was empty under --parallel

[Chemaclass]

🤔 Background

Related #1004

--report-junit, --report-tap, --report-json, --report-html and --log-junit all produced a report of zero tests whenever the run was parallel. The tests ran and passed; only the report was empty.

./bashunit --report-junit r.xml tests/unit/util              # tests="49"
./bashunit --parallel --report-junit r.xml tests/unit/util   # tests="0"

That's worse than an obviously broken file. --parallel is the mode people reach for in CI, junit is what CI consumes, and a junit file reporting no tests renders as a green, empty run. A suite could be fully green, fully reported, and communicating nothing.

🔍 Cause

reports::add_test is called from runner/exec.sh, which under --parallel runs inside the per-test worker. The arrays it appends to died with the worker, and state/parallel.sh — which rebuilds counters from the .result files — had no knowledge of them. Counters crossed the fork boundary; report rows did not.

💡 Fix

Each row is also spooled to a run-scoped file — the same mechanism --snapshot-report-unused already uses to cross that boundary — and replayed in the parent immediately before the writers run. Fields are base64-encoded because a failure message carries newlines and arbitrary text.

The arrays are still filled rather than skipped when parallel. My first version returned early there, and 32 reports unit tests started failing — they call add_test directly in the parent and assert the arrays. The parent never reaches that path for a real parallel test, so replaying the spool cannot double-count.

✅ Verification

All three text reports generated from one fixture both ways and compared: junit identical; tap and json identical in content, differing only in row order, which is inherent to parallel execution. Statuses, durations, assertion counts and the multi-line failure message all survive.

The new acceptance test runs the same suite both ways and compares counts, so they cannot drift apart again.

make sa · make lint · bash build.sh bin -v → ✅ Build verified ✅ · fork budget unchanged · 1735 sequential / 1694 parallel-simple-strict.