feat(import): add Label field support for high-cardinality per-row data

Add support for Label-kind categories to handle high-cardinality
per-row fields like descriptions, IDs, and notes. These fields are
stored alongside regular categories but default to Axis::None and
are excluded from pivot category limits.

Changes:
- analyzer.rs: Label fields now default to accepted=true
- wizard.rs: Collect and process label fields during model building,
  attaching label values as coordinates for each cell
- category.rs: Add Label variant to CategoryKind enum
- types.rs: Add add_label_category() method and update category
  counting to only include Regular-kind categories

Co-Authored-By: fiddlerwoaroof/git-smart-commit (unsloth/Qwen3.5-35B-A3B-GGUF:Q5_K_M)

src/import/analyzer.rs

@@ -40,7 +40,7 @@ impl FieldProposal {
             FieldKind::Category => "Category (dimension)",
             FieldKind::Measure => "Measure (numeric)",
             FieldKind::TimeCategory => "Time Category",
-            FieldKind::Label => "Label/Identifier (skip)",
+            FieldKind::Label => "Label (per-row, drill-view only)",
         }
     }
 }
@@ -167,7 +167,7 @@ pub fn analyze_records(records: &[Value]) -> Vec<FieldProposal> {
                     field,
                     kind: FieldKind::Label,
                     distinct_values: distinct_vec,
-                    accepted: false,
+                    accepted: true,
                     date_format: None,
                     date_components: vec![],
                 };
@@ -178,7 +178,7 @@ pub fn analyze_records(records: &[Value]) -> Vec<FieldProposal> {
                 field,
                 kind: FieldKind::Label,
                 distinct_values: vec![],
-                accepted: false,
+                accepted: true,
                 date_format: None,
                 date_components: vec![],
             }