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_conversion.py

@@ -0,0 +1,52 @@
+import pytest
+from conftest import golden_entries, golden_manifest
+
+from target_revenue import conversion, validation
+
+
+def test_conversion_status_not_converted_partway_through():
+    manifest = golden_manifest()
+    status = conversion.conversion_status(manifest, golden_entries()[:4])
+    assert status.is_converted is False
+    assert status.outstanding_target == 45000
+
+
+def test_conversion_status_converted_after_full_sequence():
+    manifest = golden_manifest()
+    status = conversion.conversion_status(manifest, golden_entries())
+    assert status.is_converted is True
+    assert status.outstanding_target == 0
+    assert status.future_license == "MIT"
+
+
+def test_conversion_status_requires_no_attestation_document():
+    """PRD FR-7/G6: conversion status must be computable from Manifest +
+    Ledger alone, with no attestation file consulted or required."""
+    manifest = golden_manifest()
+    entries = golden_entries()
+    status_without_attestation = conversion.conversion_status(manifest, entries)
+    assert status_without_attestation.is_converted is True
+
+
+def test_generate_attestation_for_converted_phase():
+    manifest = golden_manifest()
+    entries = golden_entries()
+    attestation = conversion.generate_attestation(
+        manifest, entries, conversion_timestamp="2027-06-01T00:00:00Z"
+    )
+    validation.validate_conversion_attestation(attestation)
+    assert attestation["final_outstanding_target"] == 0
+    assert attestation["final_development_credit"] == 67000
+    assert attestation["final_remission_credit"] == 33000
+    assert attestation["future_license"] == "MIT"
+    assert attestation["phase"] == "trsl:phase:example-001"
+    assert attestation["ledger_checkpoint"] == entries[-1]["id"]
+
+
+def test_generate_attestation_rejects_unconverted_phase():
+    manifest = golden_manifest()
+    partial_entries = golden_entries()[:4]  # Outstanding Target still 45000
+    with pytest.raises(ValueError, match="Outstanding Target"):
+        conversion.generate_attestation(
+            manifest, partial_entries, conversion_timestamp="2026-12-01T00:00:00Z"
+        )