feat(context): S7 — D7 context seam: OKF navigation + gated ExpeL fold

Step 1 of the loop, built from method-spec §3 alone:
- okf.py (pure stdlib): frontmatter parse, deterministic/tolerant/boundary-checked
  index navigation, bundle_context rendering with type:verdict exclusion
- experience.py: CandidateFeatures from the IR projection, §4.2 id minting,
  structural ranking (0.60·Jaccard + 0.25·type + 0.15·magnitude bucket),
  first-write-wins store, bundle seeding with the realization marker,
  fold-before-generation (empty retrieval → base unchanged)

Load-bearing (§11), each proved RED on detach: verdict-layer exclusion, fold,
seed learning fields, agent-toolkit import guard. 76/76 without an API key;
ruff + mypy --strict clean.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QdSfQdND84oeq2mbjueLTS

tests/test_okf.py

@@ -0,0 +1,202 @@
+"""OKF navigation + read-context rendering (method-spec §3 Step 1, §11).
+
+Load-bearing seams proved here:
+
+- **Verdict-layer exclusion:** the realization signal must NEVER appear in the
+  rendered read-context — prior verdicts reach the prompt ONLY via the gated
+  experience fold. The test is RED if ``type: verdict`` files leak into rendering.
+- **Context-seam purity (import guard):** the navigation/context module imports
+  no agent toolkit — and stays pure stdlib (D7-portable by design).
+"""
+
+from __future__ import annotations
+
+import ast
+import sys
+from pathlib import Path
+
+import pytest
+
+from portfolio_optimiser_claude.okf import ConceptFile, bundle_context, navigate_bundle
+
+BUNDLE = Path(__file__).resolve().parents[1] / "shared" / "examples" / "bygg-energi-mikro"
+SRC_PKG = Path(__file__).resolve().parents[1] / "src" / "portfolio_optimiser_claude"
+
+
+def _write(path: Path, text: str) -> None:
+    path.write_text(text, encoding="utf-8")
+
+
+def _make_bundle(tmp_path: Path, index_body: str, files: dict[str, str]) -> Path:
+    _write(tmp_path / "index.md", f"---\ntype: index\ntitle: Test\n---\n{index_body}\n")
+    for name, text in files.items():
+        _write(tmp_path / name, text)
+    return tmp_path
+
+
+class TestNavigation:
+    """§3 Step 1: navigate from index.md — deterministic, tolerant, boundary-checked."""
+
+    def test_missing_index_is_an_error(self, tmp_path: Path) -> None:
+        # A bundle has no entry point without index.md.
+        with pytest.raises(FileNotFoundError):
+            navigate_bundle(tmp_path)
+
+    def test_order_is_index_first_then_first_seen_deduplicated(self, tmp_path: Path) -> None:
+        bundle = _make_bundle(
+            tmp_path,
+            "See [b](b.md) then [a](a.md) then [b again](b.md).",
+            {
+                "a.md": "---\ntype: project\ntitle: A\n---\nBody A.",
+                "b.md": "---\ntype: reference\ntitle: B\n---\nBody B.",
+            },
+        )
+        names = [c.path.name for c in navigate_bundle(bundle)]
+        assert names == ["index.md", "b.md", "a.md"]
+
+    def test_out_of_bundle_and_escaping_targets_are_skipped(self, tmp_path: Path) -> None:
+        # A target containing a path separator is out-of-bundle — skipped, never
+        # raised; ../-escapes never resolve outside the bundle (fail-closed).
+        outside = tmp_path / "outside.md"
+        _write(outside, "---\ntype: project\ntitle: Outside\n---\nSecret.")
+        bundle_dir = tmp_path / "bundle"
+        bundle_dir.mkdir()
+        bundle = _make_bundle(
+            bundle_dir,
+            "Links: [up](../outside.md), [sub](sub/inner.md), [ok](a.md).",
+            {"a.md": "---\ntype: project\ntitle: A\n---\nBody A."},
+        )
+        names = [c.path.name for c in navigate_bundle(bundle)]
+        assert names == ["index.md", "a.md"]
+
+    def test_broken_link_is_tolerated_never_raised(self, tmp_path: Path) -> None:
+        bundle = _make_bundle(
+            tmp_path,
+            "Links: [gone](missing.md), [ok](a.md).",
+            {"a.md": "---\ntype: project\ntitle: A\n---\nBody A."},
+        )
+        names = [c.path.name for c in navigate_bundle(bundle)]
+        assert names == ["index.md", "a.md"]
+
+    def test_shared_bundle_navigates_all_linked_concepts(self) -> None:
+        # Integration on the shared example bundle: every index-linked file is
+        # reached exactly once; the out-of-bundle ../../README.md link is skipped.
+        names = [c.path.name for c in navigate_bundle(BUNDLE)]
+        assert names[0] == "index.md"
+        assert len(names) == len(set(names))
+        assert set(names) == {
+            "index.md",
+            "bygg-kontor-nord.md",
+            "tiltak-led-retrofit.md",
+            "metode-ipmvp-a.md",
+            "kilder-realiseringsgap.md",
+            "verdict-led-fro.md",
+        }
+
+
+class TestFrontmatter:
+    """§3 Step 1: leading ``---`` block, line-oriented ``key: value``; ``type`` required."""
+
+    def test_missing_type_is_an_error(self, tmp_path: Path) -> None:
+        _write(tmp_path / "index.md", "---\ntitle: No type\n---\nBody.")
+        with pytest.raises(ValueError, match="type"):
+            navigate_bundle(tmp_path)
+
+    def test_unknown_fields_preserved_and_quotes_stripped(self, tmp_path: Path) -> None:
+        _write(
+            tmp_path / "index.md",
+            '---\ntype: index\ntitle: "Quoted title"\ncustom_field: kept\n---\nBody.',
+        )
+        index = navigate_bundle(tmp_path)[0]
+        assert isinstance(index, ConceptFile)
+        assert index.type == "index"
+        assert index.title == "Quoted title"
+        assert index.frontmatter["custom_field"] == "kept"
+
+
+class TestRendering:
+    """§3 Step 1: index body first, then ``## {type}: {title}`` sections."""
+
+    def test_sections_are_typed_and_titled_after_index_body(self, tmp_path: Path) -> None:
+        bundle = _make_bundle(
+            tmp_path,
+            "The summary.\n\nSee [a](a.md).",
+            {"a.md": "---\ntype: project\ntitle: Building A\n---\nProject body."},
+        )
+        context = bundle_context(bundle)
+        assert context.startswith("The summary.")
+        assert "## project: Building A" in context
+        assert "Project body." in context
+
+    def test_empty_sections_are_dropped(self, tmp_path: Path) -> None:
+        bundle = _make_bundle(
+            tmp_path,
+            "Summary. See [empty](empty.md).",
+            {"empty.md": "---\ntype: reference\ntitle: Empty\n---\n"},
+        )
+        context = bundle_context(bundle)
+        assert "## reference: Empty" not in context
+
+
+class TestVerdictLayerExclusion:
+    """LOAD-BEARING (§3 Step 1, §11): verdicts never leak via the read-context."""
+
+    def test_navigable_verdict_is_excluded_from_rendering(self, tmp_path: Path) -> None:
+        # Control + seam in one: the verdict file IS navigable (so exclusion is
+        # doing real work), yet its unique marker never reaches the read-context.
+        # RED if rendering stops gating on ``type: verdict``.
+        marker = "UNIQUE-REALIZATION-MARKER-0.82"
+        bundle = _make_bundle(
+            tmp_path,
+            "Summary. See [v](v.md) and [a](a.md).",
+            {
+                "v.md": f"---\ntype: verdict\ntitle: Seed\n---\nSignal: {marker}.",
+                "a.md": "---\ntype: project\ntitle: A\n---\nBody A.",
+            },
+        )
+        navigated = [c.path.name for c in navigate_bundle(bundle)]
+        assert "v.md" in navigated
+        context = bundle_context(bundle)
+        assert marker not in context
+        assert "## verdict" not in context
+        assert "## project: A" in context
+
+    def test_shared_bundle_context_carries_no_realization_signal(self) -> None:
+        # The seed verdict's learning signal (realization rate 0.82, expected
+        # actual 24 600 NOK) must be absent from the rendered context — it may
+        # reach the prompt ONLY via the gated experience fold.
+        context = bundle_context(BUNDLE)
+        assert "## verdict" not in context
+        for leak in ("0.82", "0,82", "24600", "24 600", "realization_rate"):
+            assert leak not in context
+        # ...while the non-verdict concept layers ARE rendered:
+        assert "## project:" in context
+        assert "## hypothesis:" in context
+        assert "## methodology:" in context
+        assert "## reference:" in context
+
+
+def _imported_module_names(module_path: Path) -> set[str]:
+    tree = ast.parse(module_path.read_text(encoding="utf-8"))
+    names: set[str] = set()
+    for node in ast.walk(tree):
+        if isinstance(node, ast.Import):
+            names.update(alias.name.split(".")[0] for alias in node.names)
+        elif isinstance(node, ast.ImportFrom) and node.level == 0 and node.module:
+            names.add(node.module.split(".")[0])
+    return names
+
+
+class TestContextSeamPurity:
+    """LOAD-BEARING (§11): the context seam imports no agent toolkit."""
+
+    @pytest.mark.parametrize("module", ["okf.py", "experience.py"])
+    def test_context_seam_never_imports_an_agent_toolkit(self, module: str) -> None:
+        names = _imported_module_names(SRC_PKG / module)
+        assert not names & {"claude_agent_sdk", "anthropic"}
+
+    def test_okf_is_pure_stdlib(self) -> None:
+        # D7-portable by design: navigation/rendering depends on nothing beyond
+        # the standard library (relative imports would show as level > 0).
+        names = _imported_module_names(SRC_PKG / "okf.py")
+        assert names <= set(sys.stdlib_module_names)