feat: load editable prompts from markdown

tests/test_prompts.py

@@ -0,0 +1,40 @@
+from pathlib import Path
+
+import pytest
+
+from llm_trade_bot.prompts import PromptError, PromptStore
+
+
+def test_loads_named_markdown_sections(tmp_path: Path):
+    path = tmp_path / "prompts.md"
+    path.write_text(
+        "# Prompts\n\n## master_prompt\nMaster text.\n\n### Nested heading\nMore.\n\n## run_prompt\nRun text.\n",
+        encoding="utf-8",
+    )
+    prompts = PromptStore(path).load()
+    assert prompts.master_prompt == "Master text.\n\n### Nested heading\nMore."
+    assert prompts.run_prompt == "Run text."
+
+
+def test_reloads_file_for_each_snapshot(tmp_path: Path):
+    path = tmp_path / "prompts.md"
+    path.write_text("## master_prompt\nFirst\n## run_prompt\nRun", encoding="utf-8")
+    store = PromptStore(path)
+    assert store.load().master_prompt == "First"
+    path.write_text("## master_prompt\nSecond\n## run_prompt\nRun", encoding="utf-8")
+    assert store.load().master_prompt == "Second"
+
+
+@pytest.mark.parametrize(
+    "content, message",
+    [
+        ("# no sections", "level-two sections"),
+        ("## master_prompt\nMaster", "run_prompt"),
+        ("## master_prompt\nOne\n## master_prompt\nTwo\n## run_prompt\nRun", "Duplicate"),
+    ],
+)
+def test_rejects_invalid_prompt_files(tmp_path: Path, content: str, message: str):
+    path = tmp_path / "prompts.md"
+    path.write_text(content, encoding="utf-8")
+    with pytest.raises(PromptError, match=message):
+        PromptStore(path).load()