Expand material support and checkpoint the completed building toolkit

Expose the runtime block/item registry through compact material search and
single-material descriptions. Preserve private block-entity data through
checked edits and durable undo without sending payloads to model context.

Include the completed terrain tools, isolated world/map plugin, station lift,
ACP streaming and guidance fixes, local camera auto-connect, construction
scripts, and their public documentation, references and verification records.
Active station decoration and private runtime data remain outside this commit.

Validation: 145 Maven tests, 47 Bridge tests, successful camera Gradle build,
and isolated Paper verification of all 1,196 block defaults plus 5,392
independent property cases for placement, same-material edits and restoration.

scripts/test_terrain.py

@@ -0,0 +1,67 @@
+"""Regression checks for resumable local batches; no live world needed."""
+import importlib.util
+from pathlib import Path
+import tempfile
+import unittest
+from unittest.mock import patch
+
+spec = importlib.util.spec_from_file_location('terrain', Path(__file__).with_name('terrain.py'))
+terrain = importlib.util.module_from_spec(spec)
+spec.loader.exec_module(terrain)
+
+
+class BatchTests(unittest.TestCase):
+    def test_lost_apply_response_reuses_persisted_key(self):
+        with tempfile.TemporaryDirectory() as directory:
+            path = Path(directory) / 'batch.json'
+            entry = {'plan_id': 'plan', 'plan_hash': 'hash'}
+            manifest = {'tiles': [entry]}
+            calls = []
+            class Backend:
+                def call(self, method, **params):
+                    calls.append((method, params))
+                    if len(calls) == 1:
+                        raise TimeoutError('lost response')
+                    return {'operation_id': 'operation'}
+            backend = Backend()
+            with self.assertRaises(TimeoutError):
+                terrain.apply_plan(backend, entry, manifest, path)
+            saved = terrain.json.loads(path.read_text())
+            self.assertIn('idempotency_key', saved['tiles'][0])
+            with patch.object(terrain, 'finish', return_value={'status': 'applied', 'written': 7}):
+                terrain.apply_plan(backend, saved['tiles'][0], saved, path)
+            self.assertEqual(calls[0], calls[1])
+            self.assertEqual(terrain.json.loads(path.read_text())['tiles'][0]['operation_id'], 'operation')
+
+    def test_conflict_is_persisted_and_reported_not_reprepared(self):
+        with tempfile.TemporaryDirectory() as directory:
+            path = Path(directory) / 'batch.json'
+            entry = {'plan_id': 'p', 'plan_hash': 'h', 'operation_id': 'o'}
+            class Backend:
+                def call(self, *args, **kwargs):
+                    raise AssertionError('Must not start another apply')
+            with patch.object(terrain, 'finish', return_value={'status': 'conflict', 'written': 3}):
+                with self.assertRaisesRegex(RuntimeError, 'conflict'):
+                    terrain.apply_plan(Backend(), entry, {'tiles': [entry]}, path)
+            self.assertEqual(terrain.json.loads(path.read_text())['tiles'][0]['status'], 'conflict')
+
+    def test_undo_never_starts_an_unknown_apply(self):
+        with tempfile.TemporaryDirectory() as directory:
+            path = Path(directory) / 'batch.json'
+            scope = {'project_id': 'p', 'world_id': 'w', 'world_epoch': 'e'}
+            terrain.save(path, {'scope': scope, 'tiles': [{'idempotency_key': 'k', 'plan_id': 'p', 'plan_hash': 'h'}]})
+            class Backend:
+                def __init__(self, *args):
+                    pass
+                def call(self, method, **params):
+                    if method != 'project_context':
+                        raise AssertionError('Undo must not initiate a write to discover unknown apply outcome')
+                    return scope
+            args = terrain.argparse.Namespace(config=Path('unused'), console=True, manifest=path, command='undo')
+            with patch.object(terrain, 'Backend', Backend):
+                with self.assertRaisesRegex(RuntimeError, 'Uncertain apply'):
+                    terrain.run_batch(args)
+
+
+if __name__ == '__main__':
+    unittest.main()