docs: finalize Phase 0-1 validation

[brunovicco]

Summary

Finalize the Phase 0-1 validation record for the report-only Evidence-Gated Engineering Loop foundation.

• record the published harness commit and HARNESS_VERSION=1.2.1;
• record the canonical engineering-loop-schemas v0.1.2 provenance;
• document the successful repository quality gate and self-evaluation;
• distinguish contract-addressable hard gates from mandatory integrity checks;
• correct the vendoring description to reflect the deterministic, manifest-backed bundle;
• clarify that Phase 0-1 does not provide autonomous candidate creation, promotion, merge, or deployment.

This is a documentation-only change and does not alter runtime, template, plugin, security hook, or quality-gate behavior.

Change type

• Bug fix
• Feature
• Documentation
• Security or privacy hardening
• Refactoring or maintenance
• Breaking change

Validation

Validated locally with the repository environment and generated Python 3.13 profiles.

uv lock --check
uv sync --frozen --all-groups
uv run python scripts/quality_gate.py
uv run python scripts/loop_self_evaluation.py \
  --output-dir build/loop-self-evaluation
git diff --check