Add browser dashboard, run tracing, and logged navigation decisions

- dashboard.py: stdlib http.server + JSON API (tree/trace/dream/status,
  POST submit/relabel); static/ single-page Redux-DevTools-style inspector
- trace.py: runs.jsonl lifecycle events keyed by run_id
- scheduler/skills/skill: every decision carries run_id; navigation choices
  now logged (navigate:category/leaf); requeues stamp meta.parent_run
- cli: 'dashboard' subcommand; config.json untracked per-machine (see
  config.example.json)

tests/test_trace.py

@@ -0,0 +1,33 @@
+from semif_agent.trace import TraceLog
+
+
+def test_append_read_roundtrip(tmp_path):
+    trace = TraceLog(str(tmp_path / "runs.jsonl"))
+    trace.append("submit", "run-a", text="hello")
+    trace.append("queued", "run-a", weight=0.5, label="medium")
+    trace.append("submit", "run-b", text="world")
+
+    rows = trace.read()
+    assert len(rows) == 3
+    assert rows[0]["kind"] == "submit"
+    assert rows[0]["run_id"] == "run-a"
+    assert rows[0]["text"] == "hello"
+    assert rows[1]["label"] == "medium"
+
+
+def test_runs_groups_by_run_id_preserving_order(tmp_path):
+    trace = TraceLog(str(tmp_path / "runs.jsonl"))
+    trace.append("submit", "run-a", text="x")
+    trace.append("submit", "run-b", text="y")
+    trace.append("assessed", "run-a", success=True)
+
+    runs = trace.runs()
+    assert list(runs) == ["run-a", "run-b"]
+    assert len(runs["run-a"]) == 2
+    assert runs["run-b"][0]["text"] == "y"
+
+
+def test_read_missing_file_is_empty(tmp_path):
+    trace = TraceLog(str(tmp_path / "none.jsonl"))
+    assert trace.read() == []
+    assert trace.runs() == {}