chore: relicense to AGPL-3.0-or-later and add SPDX headers

Replaces LICENSE (GPLv3 -> AGPLv3) and prepends
`SPDX-License-Identifier: AGPL-3.0-or-later` to every source file
across decnet/, decnet_web/, tests/, scripts/, and tools/.

Rationale: closes the GPLv3 ASP loophole so any party operating a
modified DECNET as a network service must offer their modified
source. Personal copyright (Samuel Paschuan) + inbound=outbound
contributions make a future unilateral relicense infeasible.

- LICENSE: full AGPL-3.0 text (gnu.org/licenses/agpl-3.0.txt)
- COPYRIGHT: project copyright notice
- tools/add_spdx_headers.py: idempotent header injector
  (shebang- and PEP 263-aware)

Touches 1565 source files (.py, .ts, .tsx, .js, .jsx, .css, .sh).
No behavior change; comments only.

tests/bus/__init__.py

@@ -0,0 +1 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later

tests/bus/conftest.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """Shared fixtures for decnet.bus tests."""
 from __future__ import annotations
 

tests/bus/test_app_singleton.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """Tests for the process-wide app-bus singleton.
 
 Covers the retry-with-backoff behaviour of ``get_app_bus()`` — the

tests/bus/test_base.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """Unit tests for :mod:`decnet.bus.base` — wildcard matching and the Event envelope."""
 from __future__ import annotations
 

tests/bus/test_closed_publish.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """Tests for graceful publish-on-closed-bus behaviour.
 
 Regression guard for the 'publish on closed bus' log flood: when a

tests/bus/test_control_listener.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """Tests for :func:`run_control_listener`.
 
 The listener is the worker-side half of the Workers panel stop flow:

tests/bus/test_factory.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """Tests for :func:`decnet.bus.factory.get_bus` dispatch."""
 from __future__ import annotations
 

tests/bus/test_fake_bus.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """Tests for :class:`decnet.bus.fake.FakeBus` and :class:`NullBus`."""
 from __future__ import annotations
 

tests/bus/test_heartbeat.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """Shared ``run_health_heartbeat`` helper (DEBT-031 workers 7–9).
 
 Three workers (agent, forwarder, updater) publish identical

tests/bus/test_protocol.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """Tests for the wire protocol framing."""
 from __future__ import annotations
 

tests/bus/test_publish.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """Tests for :mod:`decnet.bus.publish`.
 
 The whole point of ``publish_safely`` is that it never raises back at the

tests/bus/test_topics.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """Tests for the topic hierarchy builders."""
 from __future__ import annotations
 

tests/bus/test_ttp_topics.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """Bus topic naming tests for the TTP family (CDD step E.2.3).
 
 Pins the wire vocabulary the worker (E.1.7), the API router (E.3.8),

tests/bus/test_unix_socket_bus.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """End-to-end tests for :class:`UnixSocketBus` against a real :class:`BusServer`.
 
 These tests run in the dev loop (no pytest marker) because they only need

tests/bus/test_worker.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """Tests for :func:`decnet.bus.worker.bus_worker` lifecycle + heartbeat."""
 from __future__ import annotations