fix: require anchored structured file edits

src/lai_automation/agent.py

@@ -35,6 +35,11 @@ Efficiency and completion rules:
 	fix to similar endpoints unless the issue requires it.
 - Preserve unrelated lines exactly. Do not reformat, rename, clean up, or correct
 	unrelated code while solving the issue.
+- For structured files such as PHP arrays, JSON, YAML, XML, and configuration,
+	use only small localized edits around a uniquely matching existing anchor.
+	Verify that the exact anchor occurs once before replacing it.
+- Never reconstruct or rewrite an entire structured file. Never use broad text
+	replacement, global substitution, or repeated delimiters as edit anchors.
 - Prefer adding a focused method to the closest existing test class over creating
 	another test file. Never declare a helper class name that already exists.
 - For every new join, inspect all key columns and cardinality. Prevent duplicate

tests/test_agent.py

@@ -24,6 +24,8 @@ def test_system_prompt_requires_precise_diff_hygiene() -> None:
     assert "Never create backup files" in _SYSTEM_TEMPLATE
     assert "failure-report transport code" in _SYSTEM_TEMPLATE
     assert "Preserve unrelated lines exactly" in _SYSTEM_TEMPLATE
+    assert "small localized edits around a uniquely matching existing anchor" in _SYSTEM_TEMPLATE
+    assert "Never reconstruct or rewrite an entire structured file" in _SYSTEM_TEMPLATE
     assert "closest existing test class" in _SYSTEM_TEMPLATE
     assert "inspect all key columns and cardinality" in _SYSTEM_TEMPLATE
     assert "remove trailing spaces" in _SYSTEM_TEMPLATE