Add replay graph core skeleton

src/comptext_v7/graph/__init__.py

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+"""Replay graph deterministic core helpers."""
+
+from .evidence import ReplayGraphDiff, compare_edges
+from .ordering import find_order_violations
+from .reachability import has_path, reachable_nodes
+from .topology import adjacency_map, nodes_from_edges, normalize_edges
+
+__all__ = [
+    "ReplayGraphDiff",
+    "adjacency_map",
+    "compare_edges",
+    "find_order_violations",
+    "has_path",
+    "nodes_from_edges",
+    "normalize_edges",
+    "reachable_nodes",
+]

src/comptext_v7/graph/evidence.py

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+"""Deterministic evidence helpers for replay graph diffs."""
+
+from __future__ import annotations
+
+from collections.abc import Iterable
+from dataclasses import dataclass
+
+from .topology import normalize_edges, nodes_from_edges
+
+
+Edge = tuple[str, str]
+
+
+@dataclass(frozen=True)
+class ReplayGraphDiff:
+    """Immutable graph-diff evidence for replay validation."""
+
+    missing_edges: tuple[Edge, ...]
+    added_edges: tuple[Edge, ...]
+    missing_nodes: tuple[str, ...]
+    added_nodes: tuple[str, ...]
+
+
+def compare_edges(
+    original_edges: Iterable[Edge],
+    replay_edges: Iterable[Edge],
+) -> ReplayGraphDiff:
+    """Compare original and replay edges and return deterministic diff evidence."""
+    original = normalize_edges(original_edges)
+    replay = normalize_edges(replay_edges)
+
+    original_set = set(original)
+    replay_set = set(replay)
+
+    missing_edges = tuple(sorted(original_set - replay_set))
+    added_edges = tuple(sorted(replay_set - original_set))
+
+    original_nodes = set(nodes_from_edges(original))
+    replay_nodes = set(nodes_from_edges(replay))
+
+    missing_nodes = tuple(sorted(original_nodes - replay_nodes))
+    added_nodes = tuple(sorted(replay_nodes - original_nodes))
+
+    return ReplayGraphDiff(
+        missing_edges=missing_edges,
+        added_edges=added_edges,
+        missing_nodes=missing_nodes,
+        added_nodes=added_nodes,
+    )

src/comptext_v7/graph/ordering.py

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+"""Deterministic ordering checks for replay sequences."""
+
+from __future__ import annotations
+
+from collections.abc import Iterable, Sequence
+
+
+Edge = tuple[str, str]
+
+
+def find_order_violations(
+    sequence: Sequence[str],
+    required_before: Iterable[Edge],
+) -> tuple[Edge, ...]:
+    """Return lexicographically sorted order violations."""
+    positions = {node: index for index, node in enumerate(sequence)}
+    violations: set[Edge] = set()
+
+    for before, after in required_before:
+        if before not in positions or after not in positions:
+            continue
+        if positions[before] > positions[after]:
+            violations.add((before, after))
+
+    return tuple(sorted(violations))

src/comptext_v7/graph/reachability.py

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+"""Deterministic reachability helpers for directed graphs."""
+
+from __future__ import annotations
+
+from collections import deque
+from collections.abc import Iterable
+
+from .topology import adjacency_map
+
+
+Edge = tuple[str, str]
+
+
+def reachable_nodes(edges: Iterable[Edge], start: str) -> tuple[str, ...]:
+    """Return sorted reachable nodes from start.
+
+    The start node is excluded unless it is reachable through a cycle.
+    """
+    adjacency = adjacency_map(edges)
+    queue: deque[str] = deque(adjacency.get(start, ()))
+    seen: set[str] = set()
+
+    while queue:
+        node = queue.popleft()
+        if node in seen:
+            continue
+        seen.add(node)
+        for neighbor in adjacency.get(node, ()):  # deterministic ordering from adjacency_map
+            if neighbor not in seen:
+                queue.append(neighbor)
+
+    if start in seen:
+        return tuple(sorted(seen))
+    return tuple(sorted(node for node in seen if node != start))
+
+
+def has_path(edges: Iterable[Edge], start: str, target: str) -> bool:
+    """Return True when a directed path exists from start to target."""
+    return target in reachable_nodes(edges, start)

src/comptext_v7/graph/topology.py

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+"""Deterministic topology helpers for replay relation graphs."""
+
+from __future__ import annotations
+
+from collections.abc import Iterable
+
+
+Edge = tuple[str, str]
+
+
+def normalize_edges(edges: Iterable[Edge]) -> tuple[Edge, ...]:
+    """Return sorted unique edges and reject self-loops."""
+    unique_edges: set[Edge] = set()
+    for source, target in edges:
+        if source == target:
+            raise ValueError(f"self-loop edge is not allowed: {source!r} -> {target!r}")
+        unique_edges.add((source, target))
+    return tuple(sorted(unique_edges))
+
+
+def nodes_from_edges(edges: Iterable[Edge]) -> tuple[str, ...]:
+    """Return sorted unique node ids derived from edges."""
+    normalized = normalize_edges(edges)
+    nodes = {source for source, _ in normalized}
+    nodes.update(target for _, target in normalized)
+    return tuple(sorted(nodes))
+
+
+def adjacency_map(edges: Iterable[Edge]) -> dict[str, tuple[str, ...]]:
+    """Return deterministic adjacency lists keyed by node id."""
+    normalized = normalize_edges(edges)
+    adjacency: dict[str, list[str]] = {}
+    for source, target in normalized:
+        adjacency.setdefault(source, []).append(target)
+        adjacency.setdefault(target, [])
+
+    return {
+        node: tuple(sorted(neighbors))
+        for node, neighbors in sorted(adjacency.items())
+    }

tests/test_replay_graph_core.py

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+from __future__ import annotations
+
+import pytest
+
+from src.comptext_v7.graph import (
+    ReplayGraphDiff,
+    adjacency_map,
+    compare_edges,
+    find_order_violations,
+    has_path,
+    nodes_from_edges,
+    normalize_edges,
+    reachable_nodes,
+)
+
+
+def test_normalize_edges_removes_duplicates_and_sorts() -> None:
+    edges = [("b", "c"), ("a", "b"), ("b", "c")]
+    assert normalize_edges(edges) == (("a", "b"), ("b", "c"))
+
+
+def test_normalize_edges_rejects_self_loop() -> None:
+    with pytest.raises(ValueError):
+        normalize_edges([("n1", "n1")])
+
+
+def test_nodes_from_edges_returns_sorted_nodes() -> None:
+    edges = [("b", "c"), ("a", "b")]
+    assert nodes_from_edges(edges) == ("a", "b", "c")
+
+
+def test_adjacency_map_is_deterministic() -> None:
+    edges = [("b", "c"), ("a", "b"), ("a", "c")]
+    assert adjacency_map(edges) == {
+        "a": ("b", "c"),
+        "b": ("c",),
+        "c": (),
+    }
+
+
+def test_find_order_violations_detects_reversed_and_sorts() -> None:
+    sequence = ["c", "b", "a"]
+    required = [("a", "b"), ("b", "c"), ("x", "a")]
+    assert find_order_violations(sequence, required) == (("a", "b"), ("b", "c"))
+
+
+def test_find_order_violations_ignores_missing_nodes() -> None:
+    sequence = ["a", "b"]
+    required = [("x", "b"), ("a", "y")]
+    assert find_order_violations(sequence, required) == ()
+
+
+def test_reachable_nodes_and_path_on_connected_graph() -> None:
+    edges = [("a", "b"), ("b", "d"), ("a", "c")]
+    assert reachable_nodes(edges, "a") == ("b", "c", "d")
+    assert has_path(edges, "a", "d") is True
+    assert has_path(edges, "c", "d") is False
+
+
+def test_reachable_nodes_handles_disconnected_graph() -> None:
+    edges = [("a", "b"), ("x", "y")]
+    assert reachable_nodes(edges, "a") == ("b",)
+    assert reachable_nodes(edges, "z") == ()
+
+
+def test_reachable_nodes_includes_start_when_cycle_exists() -> None:
+    edges = [("a", "b"), ("b", "a")]
+    assert reachable_nodes(edges, "a") == ("a", "b")
+    assert has_path(edges, "a", "a") is True
+
+
+def test_compare_edges_detects_edge_and_node_diffs_deterministically() -> None:
+    original = [("a", "b"), ("b", "c"), ("d", "e")]
+    replay = [("a", "b"), ("b", "d"), ("x", "y")]
+
+    diff = compare_edges(original, replay)
+
+    assert diff == ReplayGraphDiff(
+        missing_edges=(("b", "c"), ("d", "e")),
+        added_edges=(("b", "d"), ("x", "y")),
+        missing_nodes=("c", "e"),
+        added_nodes=("x", "y"),
+    )
+    assert isinstance(diff.missing_edges, tuple)
+    assert isinstance(diff.added_nodes, tuple)