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)

semif_agent/trace.py

@@ -0,0 +1,44 @@
+"""Run lifecycle tracing: the events around each request's trip through the
+scheduler.
+
+Decision rows live in `decisions.jsonl` (SemIf-compatible). Lifecycle events
+(submit, dropped, queued, preempted, assessed, requeued, ...) live here in
+`runs.jsonl`, keyed by `run_id` (the request id) so the dashboard can rebuild
+each run's flow without touching the decision-log contract. Both files are
+append-only; replays read them in order.
+"""
+
+from __future__ import annotations
+
+import json
+import time
+from pathlib import Path
+
+
+class TraceLog:
+    def __init__(self, path: str = "data/runs.jsonl"):
+        self.path = Path(path)
+
+    def append(self, kind: str, run_id: str, **fields) -> None:
+        row = {"kind": kind, "run_id": run_id, "ts": time.time(), **fields}
+        self.path.parent.mkdir(parents=True, exist_ok=True)
+        with self.path.open("a") as handle:
+            handle.write(json.dumps(row) + "\n")
+
+    def read(self) -> list[dict]:
+        if not self.path.is_file():
+            return []
+        rows = []
+        with self.path.open("r") as handle:
+            for line in handle:
+                line = line.strip()
+                if line:
+                    rows.append(json.loads(line))
+        return rows
+
+    def runs(self) -> dict[str, list[dict]]:
+        """Group events by run_id, preserving insertion order of first sighting."""
+        grouped: dict[str, list[dict]] = {}
+        for row in self.read():
+            grouped.setdefault(row.get("run_id", ""), []).append(row)
+        return grouped