Phase 0d - Test corpus tooling (done)

Two pieces, both from D042 and D044:

Why early, and why it partly changes phase 0. A test app we compile ourselves is a real container with clean provenance - we wrote the source, so we know exactly what is in it. That is better input for the parser than a byte-crafted fixture for the happy path. Synthetic fixtures remain necessary for the malformed cases a compiler will never emit.

Observable result: orbistoun-cli corpus sync populates titles/ reproducibly on a clean machine, and one genuine container exists to point the parser at.

Done, and the marker was stale rather than the work missing

Checked against the four things this item actually asked for, on 2026-09-03:

The second half - toolchain setup plus one minimal test app built with the open toolchain - is the second source: obSCEne, which is our own source built with an open toolchain and which orbistoun runs through twenty-seven conformance sections. A real container with clean provenance, which is the whole reason this phase was pulled early.

Nothing was built to close this. The item had been finished and its marker never moved, which made the roadmap report one red phase that was not red. Fourth stale work item found this week, after /dev/random, the differential's "missing" cases, and D488's note that the oscillation does not move the verdict.