Reorganize task categories from opaque a/b to descriptive names

Replace category_a/category_b directories with algorithm, pipeline,
environment, filesystem, and process. Add separate mode field (solve/convert)
to decouple orchestration from capability grouping. Add per-category
summary and questionnaire breakdowns to both terminal report and HTML export.

lush_bench/models.py

@@ -36,15 +36,17 @@ class TestCase:
 @dataclass
 class Task:
     name: str
-    category: str  # "a" or "b"
+    category: str  # "algorithm", "pipeline", "environment", "filesystem", "process"
     description: str
     test_cases: list[TestCase]
-    bash_source: str | None = None  # category B only
+    mode: str = "solve"  # "solve" or "convert"
+    bash_source: str | None = None  # convert mode only
 
     def to_dict(self) -> dict[str, Any]:
         d: dict[str, Any] = {
             "name": self.name,
             "category": self.category,
+            "mode": self.mode,
             "description": self.description,
             "test_cases": [tc.to_dict() for tc in self.test_cases],
         }
@@ -59,6 +61,7 @@ class Task:
             category=d["category"],
             description=d["description"],
             test_cases=[TestCase.from_dict(tc) for tc in d["test_cases"]],
+            mode=d.get("mode", "solve"),
             bash_source=d.get("bash_source"),
         )
 
@@ -180,16 +183,18 @@ class QuestionnaireResponse:
 class BenchmarkResult:
     task_name: str
     category: str
-    provider: str
-    model: str
-    timestamp: str
-    bash_result: LanguageResult | None
-    lush_result: LanguageResult | None
+    mode: str = "solve"  # "solve" or "convert"
+    provider: str = ""
+    model: str = ""
+    timestamp: str = ""
+    bash_result: LanguageResult | None = None
+    lush_result: LanguageResult | None = None
 
     def to_dict(self) -> dict[str, Any]:
         return {
             "task_name": self.task_name,
             "category": self.category,
+            "mode": self.mode,
             "provider": self.provider,
             "model": self.model,
             "timestamp": self.timestamp,
@@ -202,6 +207,7 @@ class BenchmarkResult:
         return cls(
             task_name=d["task_name"],
             category=d["category"],
+            mode=d.get("mode", "solve"),
             provider=d["provider"],
             model=d["model"],
             timestamp=d["timestamp"],