feat(phase2): llm report writer (P5.3)

- New module src/pf1e_simulator/report.py with ReportContext, build_report_context,
  LLMReportPolicy, ReportBudget, format_llm_report, build_report_prompt
- Prompt pack fixture: tests/fixtures/prompt_pack_fs/report.md (FR narrator)
- CLI integration: --llm-report + --output flags, mutually exclusive with --transcript
- Budget enforcement: ReportBudget integrates with CostBudget, allows max_retries+1 calls
- Tests: test_report_context, test_report_prompt_pack, test_llm_report_policy,
  test_format_llm_report, test_cli_llm_report, test_report_budget (27 new tests)

tests/test_cli_llm_report.py

@@ -0,0 +1,62 @@
+"""CLI integration test for --llm-report flag (P5.3 T5)."""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+import pytest
+
+from pf1e_simulator.cli import main
+
+ROOT = Path(__file__).resolve().parents[1]
+MAP = ROOT / "data" / "maps" / "sample_arena.yaml"
+
+
+def _argv_common() -> list[str]:
+    return [
+        "--map", str(MAP),
+        "--side", "players", str(ROOT / "data" / "monsters" / "goblin.json"),
+        "--side", "monsters", str(ROOT / "data" / "monsters" / "orc.json"),
+    ]
+
+
+def test_cli_llm_report_mutually_exclusive_with_transcript() -> None:
+    """--llm-report and --transcript are mutually exclusive."""
+    argv = [*_argv_common(), "--llm-report", "--transcript"]
+
+    with pytest.raises(SystemExit) as exc_info:
+        main(argv)
+    assert exc_info.value.code == 2
+
+
+def test_cli_output_requires_llm_report() -> None:
+    """--output requires --llm-report."""
+    argv = [*_argv_common(), "--output", "report.md"]
+
+    with pytest.raises(SystemExit) as exc_info:
+        main(argv)
+    assert exc_info.value.code == 2
+
+
+def test_cli_llm_report_requires_api_key_env(monkeypatch: pytest.MonkeyPatch) -> None:
+    """--llm-report fails gracefully when PF1E_LLM_API_KEY not set."""
+    monkeypatch.delenv("PF1E_LLM_API_KEY", raising=False)
+    monkeypatch.delenv("PF1E_PROMPT_PACK_DIR", raising=False)
+
+    argv = [*_argv_common(), "--llm-report"]
+
+    with pytest.raises(SystemExit) as exc_info:
+        main(argv)
+    assert exc_info.value.code == 2
+
+
+def test_cli_llm_report_requires_prompt_pack_dir(monkeypatch: pytest.MonkeyPatch) -> None:
+    """--llm-report fails gracefully when PF1E_PROMPT_PACK_DIR not set."""
+    monkeypatch.setenv("PF1E_LLM_API_KEY", "test-key")
+    monkeypatch.delenv("PF1E_PROMPT_PACK_DIR", raising=False)
+
+    argv = [*_argv_common(), "--llm-report"]
+
+    with pytest.raises(SystemExit) as exc_info:
+        main(argv)
+    assert exc_info.value.code == 2