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_manifest_validation.py

@@ -0,0 +1,61 @@
+import copy
+
+import pytest
+from conftest import golden_manifest
+
+from target_revenue import validation
+
+
+def test_golden_manifest_is_conformant():
+    validation.validate_phase_manifest(golden_manifest())
+
+
+def test_manifest_missing_longstop_is_rejected():
+    manifest = copy.deepcopy(golden_manifest())
+    del manifest["phase"]["longstop_at"]
+    with pytest.raises(validation.ConformanceError):
+        validation.validate_phase_manifest(manifest)
+
+
+def test_manifest_bad_future_license_is_rejected():
+    manifest = copy.deepcopy(golden_manifest())
+    manifest["phase"]["future_license"] = "GPL-3.0"
+    with pytest.raises(validation.ConformanceError):
+        validation.validate_phase_manifest(manifest)
+
+
+def test_manifest_missing_required_field_is_rejected():
+    manifest = copy.deepcopy(golden_manifest())
+    del manifest["phase"]["initial_target"]
+    with pytest.raises(validation.ConformanceError):
+        validation.validate_phase_manifest(manifest)
+
+
+def test_manifest_rejects_unknown_top_level_field():
+    manifest = copy.deepcopy(golden_manifest())
+    manifest["unexpected_field"] = True
+    with pytest.raises(validation.ConformanceError):
+        validation.validate_phase_manifest(manifest)
+
+
+def test_initial_target_amount_immutable_across_versions():
+    published = golden_manifest()
+    candidate = copy.deepcopy(published)
+    candidate["phase"]["initial_target"]["amount"] = 70000
+    errors = validation.check_manifest_immutability(published, candidate)
+    assert errors, "reducing initial_target.amount must be flagged"
+    assert "initial_target.amount" in errors[0]
+
+
+def test_phase_id_immutable_across_versions():
+    published = golden_manifest()
+    candidate = copy.deepcopy(published)
+    candidate["phase"]["id"] = "trsl:phase:example-002"
+    errors = validation.check_manifest_immutability(published, candidate)
+    assert errors
+    assert "phase.id" in errors[0]
+
+
+def test_unchanged_manifest_has_no_immutability_violations():
+    manifest = golden_manifest()
+    assert validation.check_manifest_immutability(manifest, manifest) == []