Implement TREV-WP-0002 Stage 0 foundation: schemas, pure fold, golden Phase

Delivers the offline runnable specification foundation for the Trust Layer
(TSD §3-§6), not a hosted Trust Service:

- JSON Schemas for Phase Manifest, Ledger Entry, Extension Contract, and
  Conversion Attestation, encoding the Stage 0 working defaults (Q3 future
  license enum, Q6 single-currency Phases, Q8 required longstop_at).
- src/target_revenue: pure Outstanding Target fold, SHA-256 hash-chain
  verification, Ed25519 signing helpers, extension conformance checks
  (including a core-term-redefinition heuristic), and conversion detection
  that never requires an attestation document to determine conversion status.
- examples/phase-001: golden Phase package matching the concept doc's
  worked example, generated via scripts/generate_golden_phase.py so the
  hash chain is computed by the library itself, not hand-typed.
- 32 passing pytest tests covering manifest/ledger/extension conformance,
  tamper/reorder detection, and the full lifecycle fold to conversion.
- docs/adr/ADR-0001: proposed (not accepted) Stage 0 stack choice, per the
  WP-0002-T01 human-accept gate — implementation proceeded against the
  proposal as the workplan note permits, but the task stays open.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

tests/test_extension_conformance.py

@@ -0,0 +1,55 @@
+import copy
+
+import pytest
+from conftest import golden_extension, load_json, FIXTURES_DIR
+
+from target_revenue import validation
+
+
+@pytest.mark.parametrize(
+    "name",
+    [
+        "development-license",
+        "cost-plus-operations",
+        "phase-sponsorship",
+        "service-with-development-allocation",
+    ],
+)
+def test_canonical_stage0_extensions_are_conformant(name):
+    validation.validate_extension_contract(golden_extension(name))
+
+
+def test_non_conforming_extension_is_rejected():
+    extension = load_json(FIXTURES_DIR / "non_conforming_extension.json")
+    with pytest.raises(validation.ConformanceError) as excinfo:
+        validation.validate_extension_contract(extension)
+    assert "Outstanding Target" in str(excinfo.value)
+
+
+def test_extension_missing_required_field_is_rejected():
+    extension = copy.deepcopy(golden_extension("development-license"))
+    del extension["evidence"]
+    with pytest.raises(validation.ConformanceError):
+        validation.validate_extension_contract(extension)
+
+
+def test_extension_bad_status_is_rejected():
+    extension = copy.deepcopy(golden_extension("development-license"))
+    extension["status"] = "endorsed"  # not in {registered, canonical, deprecated}
+    with pytest.raises(validation.ConformanceError):
+        validation.validate_extension_contract(extension)
+
+
+def test_core_term_redefinition_heuristic_is_case_insensitive():
+    extension = copy.deepcopy(golden_extension("development-license"))
+    extension["allocation"]["rule"] = "Development Credit means whatever the licensor prefers."
+    errors = validation.check_extension_core_term_redefinition(extension)
+    assert errors
+    assert "Development Credit" in errors[0]
+
+
+def test_legitimate_rule_referencing_core_term_without_redefining_is_allowed():
+    extension = golden_extension("development-license")
+    # References "Development Credit" as a target, not a redefinition.
+    errors = validation.check_extension_core_term_redefinition(extension)
+    assert errors == []