feat: MGTP minimal deterministic decision artefact demo

[Copilot]

Adds a minimal, regulator-readable artefact demonstration proving deterministic canonicalisation, hash stability, and replay correctness for the MGTP commit gate — with no changes to any upstream module.

New files

• examples/minimal_decision_demo.py — Fixed-input demo (no randomness, no live timestamps). Evaluates a canonical CommitRequest, prints verdict, decision_hash, and canonical_bytes (base64):

  verdict        : ALLOW
  decision_hash  : fab8740c920489154038063620e1453460e1ea1549d0cb1f0cb2dca0ce860360
  canonical_bytes (base64): eyJhcnRlZmFjdF92ZXJzaW9uIjoiMC4x…
  

  Reproduce: python examples/minimal_decision_demo.py

• tests/fixtures/golden_canonical_bytes.b64 — Locked golden canonical bytes for the fixed input set.

• tests/test_replay_decision.py — Two replay assertions:

  • T-REPLAY-1: canonicalise(evaluate(REQUEST, RULESET)) is byte-identical to the golden fixture (any byte difference → fail).
  • T-REPLAY-2: decision_hash in re-evaluated result matches hash embedded in golden bytes.

Modified files

• README.md — New Deterministic Decision Artefact Demo section: input table, output artefact snippet, decision_hash, and exact reproduce/replay commands.

• .github/workflows/ci.yml — Added check-mode step running python examples/minimal_decision_demo.py across the Python 3.10/3.11/3.12 matrix on every push/PR.

• .gitignore — Excludes __pycache__, .pyc, .pytest_cache.

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[Copilot]

Pull request overview

Adds a deterministic “decision artefact” demo + golden-fixture replay tests to prove canonicalisation stability and decision hash replay for the MGTP/commit_gate commit authority evaluation, and wires the demo into CI.

Changes:

• Add a fixed-input demo script that prints the evaluated verdict + canonical artefact bytes (base64).
• Add golden canonical bytes + replay tests asserting byte-identical canonicalisation and stable decision_hash.
• Document the demo/replay steps in README and run the demo in CI.

Reviewed changes

Copilot reviewed 5 out of 34 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tests/test_replay_decision.py	Adds two replay tests (byte-identical canonical bytes + decision_hash match).
tests/fixtures/golden_canonical_bytes.b64	Stores the locked “golden” canonical bytes fixture (base64).
examples/minimal_decision_demo.py	Deterministic demo that evaluates a fixed request/ruleset and prints canonical bytes (base64).
README.md	Documents deterministic artefact demo inputs, expected outputs, and replay commands.
.github/workflows/ci.yml	Runs the demo script as an additional CI step across the Python matrix.
.gitignore	Adds ignores for Python bytecode/caches and build artefacts.
tests/pycache/test_smoke_mgtp.cpython-312-pytest-9.0.2.pyc	Compiled artefact accidentally committed (should be removed from git).
pycache/stop_machine.cpython-312.pyc	Compiled artefact accidentally committed (should be removed from git).
pycache/authority_gate.cpython-312.pyc	Compiled artefact accidentally committed (should be removed from git).
pycache/invariant_litmus.cpython-312.pyc	Compiled artefact accidentally committed (should be removed from git).
pycache/test_stop_machine.cpython-312-pytest-9.0.2.pyc	Compiled artefact accidentally committed (should be removed from git).
pycache/test_authority_gate.cpython-312-pytest-9.0.2.pyc	Compiled artefact accidentally committed (should be removed from git).
commit_gate/src/commit_gate/pycache/engine.cpython-312.pyc	Compiled artefact accidentally committed (should be removed from git).
commit_gate/src/commit_gate/pycache/drift.cpython-312.pyc	Compiled artefact accidentally committed (should be removed from git).
commit_gate/src/commit_gate/pycache/canonicalise.cpython-312.pyc	Compiled artefact accidentally committed (should be removed from git).
commit_gate/src/commit_gate/pycache/init.cpython-312.pyc	Compiled artefact accidentally committed (should be removed from git).
commit_gate/tests/pycache/test_determinism.cpython-312-pytest-9.0.2.pyc	Compiled artefact accidentally committed (should be removed from git).
commit_gate/tests/pycache/test_drift.cpython-312-pytest-9.0.2.pyc	Compiled artefact accidentally committed (should be removed from git).
prometheus/tests/pycache/conftest.cpython-312-pytest-9.0.2.pyc	Compiled artefact accidentally committed (should be removed from git).
prometheus/tests/pycache/init.cpython-312.pyc	Compiled artefact accidentally committed (should be removed from git).
prometheus/tests/pycache/test_schema_validation.cpython-312-pytest-9.0.2.pyc	Compiled artefact accidentally committed (should be removed from git).
prometheus/tests/pycache/test_redline_scanner.cpython-312-pytest-9.0.2.pyc	Compiled artefact accidentally committed (should be removed from git).
prometheus/tests/pycache/test_negative_injection.cpython-312-pytest-9.0.2.pyc	Compiled artefact accidentally committed (should be removed from git).
prometheus/tests/pycache/test_input_hashing.cpython-312-pytest-9.0.2.pyc	Compiled artefact accidentally committed (should be removed from git).
prometheus/tests/pycache/test_fit_report_classification.cpython-312-pytest-9.0.2.pyc	Compiled artefact accidentally committed (should be removed from git).
prometheus/tests/pycache/test_aggregation_determinism.cpython-312-pytest-9.0.2.pyc	Compiled artefact accidentally committed (should be removed from git).
prometheus/src/prometheus/pycache/schemas.cpython-312.pyc	Compiled artefact accidentally committed (should be removed from git).
prometheus/src/prometheus/pycache/redlines.cpython-312.pyc	Compiled artefact accidentally committed (should be removed from git).
prometheus/src/prometheus/pycache/io_jsonl.cpython-312.pyc	Compiled artefact accidentally committed (should be removed from git).
prometheus/src/prometheus/pycache/hashing.cpython-312.pyc	Compiled artefact accidentally committed (should be removed from git).
prometheus/src/prometheus/pycache/fit_report.cpython-312.pyc	Compiled artefact accidentally committed (should be removed from git).
prometheus/src/prometheus/pycache/aggregate.cpython-312.pyc	Compiled artefact accidentally committed (should be removed from git).
prometheus/src/prometheus/pycache/init.cpython-312.pyc	Compiled artefact accidentally committed (should be removed from git).

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[Copilot]

This script runs significant logic at import time (evaluate + printing). Wrapping execution in a main() and guarding with if name == 'main' avoids side effects if the module is imported (e.g., by tooling) and makes it easier to reuse in tests.

[Copilot]

For deterministic behavior across environments, consider specifying an explicit encoding when reading the fixture (it's ASCII/base64) and using base64.b64decode(..., validate=True) so corruption/non-base64 characters fail loudly with a clear error.