nisse-core: group modules into packages by architecture section

A pure move; behaviour unchanged.

- models (L9, L7): llm, catalog, probe, render, render_anthropic, context
- log (L7, L6): canonical, views
- state (L8): store (was state), reconcile, worker, cancel, dump
- knowledge (L10, L6.4): vault, memory
- conversation (L5): transport, matrix
- execution (L13): ssh (was execution), testing
- authority (P3, P4, L4): actions
- gitea, oplog, envfile stay at the top until each gains a second module.

Every import, monkeypatch target, script and doc reference rewritten.

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

nisse-core/tests/test_execution.py

@@ -5,7 +5,7 @@ from pathlib import Path
 
 import pytest
 
-from nisse_core.execution import REDACTED, HostUnavailable, SSHHost, redact
+from nisse_core.execution.ssh import REDACTED, HostUnavailable, SSHHost, redact
 
 
 def test_exit_codes_and_streams_come_back(ssh_host: SSHHost) -> None:
@@ -82,7 +82,7 @@ def test_a_changed_host_key_is_its_own_failure_and_only_forgetting_clears_it(
 ) -> None:
     import subprocess
 
-    from nisse_core.execution import HostKeyChanged
+    from nisse_core.execution.ssh import HostKeyChanged
 
     host = SSHHost(
         ssh_host.address,