M7.1: extract nisse-core

What isn't the dev agent's moves to nisse-core, unchanged in behaviour,
with its tests: canonical, render, render_anthropic, llm, catalog, probe,
context, views, state, reconcile, worker, cancel, dump, transport, matrix,
execution, testing, vault, memory, oplog, envfile and gitea (whole).

- nisse_core.state.StateStore holds the tables every agent has; an
  agent's subclass adds its tables (version, migrations), roles and
  views. nisse_dev.state.StateStore adds the build VM blocks (v5).
- views.project takes what each role is shown, rather than a fixed table.
- Vault takes the agent's name (agent=), for provenance.
- A test that nisse_core never imports an agent.
- The loop, config, git, delegation, expert, tools and evals stay in
  nisse-dev until nisse-ops has a loop to share.

Docs: the Development Plan marks M7.1 done and notes that Phase 6 waits on
the agent host and Terraform; Architecture Part L names the package.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01J5Utyfzw7gF7UhjRDEtjTk

nisse-core/src/nisse_core/cancel.py

@@ -0,0 +1,40 @@
+"""The operator's kill switch, as the working loops see it (architecture L2).
+
+`stop` has to reach work that is already running, from a thread that is not
+running it. So it is a flag, set by whoever hears the command and checked by
+the loops at each tool boundary. Setting it touches nothing durable: the
+record of a stop is written by the worker when the stopped work returns.
+"""
+
+import threading
+
+from nisse_core.canonical import ToolCall, ToolResult
+from nisse_core.state import Transcript
+
+STOPPED_RESULT = "not run: the operator stopped the agent"
+
+
+class Cancel:
+    def __init__(self) -> None:
+        self._event = threading.Event()
+
+    def set(self) -> None:
+        self._event.set()
+
+    def clear(self) -> None:
+        self._event.clear()
+
+    @property
+    def requested(self) -> bool:
+        return self._event.is_set()
+
+
+def skip_calls(
+    transcript: Transcript, calls: list[ToolCall], reason: str = STOPPED_RESULT
+) -> None:
+    """Record calls left unrun. Every tool call needs a result for the
+    transcript to render again, and the result says what happened."""
+    for call in calls:
+        transcript.append(
+            ToolResult(call_id=call.call_id, result=reason, success=False)
+        )