Harness foundation: INTENT, ADR-001, architecture, prototype adoption

- INTENT.md: three-layer model (blueprint/instance/harness), single
  shared runtime, never-become boundaries
- ADR-001 (accepted): DEC-2026-002 resolution — one harness repo for
  all projects; instances are declarative state in consuming repos
- docs/architecture.md: components, contracts (manifest, tool
  profiles, completion events, credential lanes), deployment shape
- agent_harness/: executor-worker prototype adopted and renamed
  (6/6 tests green); HARNESS-WP-0001 initial workplan (7 tasks)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

agent_harness/hub.py

@@ -0,0 +1,54 @@
+"""Custodian State Hub reporting (REST, no MCP).
+
+STATE_HUB_URL defaults to the workstation-local hub; on Railiance the
+ops-bridge tunnel exposes it at http://127.0.0.1:18000.
+"""
+
+from __future__ import annotations
+
+import os
+from typing import Any
+
+import httpx
+
+_DEFAULT_URL = "http://127.0.0.1:8000"
+_TIMEOUT = 10.0
+
+
+def _base_url() -> str:
+    return os.environ.get("STATE_HUB_URL", _DEFAULT_URL).rstrip("/")
+
+
+def post_progress_event(
+    summary: str,
+    event_type: str,
+    detail: dict[str, Any],
+    task_id: str | None = None,
+) -> bool:
+    payload: dict[str, Any] = {
+        "summary": summary,
+        "event_type": event_type,
+        "detail": detail,
+        "author": "agt-executor-worker",
+    }
+    if task_id:
+        payload["task_id"] = task_id
+    try:
+        resp = httpx.post(f"{_base_url()}/progress/", json=payload, timeout=_TIMEOUT)
+        resp.raise_for_status()
+        return True
+    except httpx.HTTPError:
+        return False
+
+
+def close_task(task_id: str) -> bool:
+    try:
+        resp = httpx.patch(
+            f"{_base_url()}/tasks/{task_id}",
+            json={"status": "done"},
+            timeout=_TIMEOUT,
+        )
+        resp.raise_for_status()
+        return True
+    except httpx.HTTPError:
+        return False