Add a bundle-backed config: dataset as smoke.hdb via git-lfs

Exercises the provider bundle path — verify sha256, unpack to the
content-addressed cache, symlink in at mount="data" so the config metadata_csv
path resolves. The loose-file config stays alongside it as the plain case.

.gitattributes

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+*.hdb filter=lfs diff=lfs merge=lfs -text
+*.hrb filter=lfs diff=lfs merge=lfs -text
+*.hdb binary
+*.hrb binary

configs/tabular_bundle.hcf

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+{
+  "_notes": [
+    "Bundle-backed variant of tabular_smoke: the dataset arrives as smoke.hdb",
+    "rather than as loose files. mount='data' places the bundle's smoke/labels.csv",
+    "at data/smoke/labels.csv, which is what metadata_csv below expects."
+  ],
+  "run_name": "tabular_bundle",
+  "num_classes": 2,
+  "split_identity_level": 1,
+  "eval_stage": "cd_fuse",
+  "save_predictions": true,
+  "seed": 1234,
+  "folds": 3,
+  "fold_seed": 100,
+  "output_root": "results",
+  "data": {
+    "module": "hypertower_core.profiles.generic",
+    "args": {
+      "metadata_csv": "data/smoke/labels.csv",
+      "id_column": "sample_id",
+      "label_col": "diagnosis",
+      "target_type": "classification",
+      "group_column": "patient_id",
+      "cat_cols": [
+        "site"
+      ],
+      "exclude_cols": [
+        "notes"
+      ]
+    }
+  },
+  "towers": [
+    {
+      "name": "cd",
+      "module": "hypertower_core.components.towers.clinical_tower",
+      "class": "ClinicalEncoder",
+      "data_source": "matrix",
+      "args": {
+        "hidden_dim": 64
+      }
+    }
+  ],
+  "stages": [
+    {
+      "name": "cd_warm",
+      "type": "warm",
+      "tower": "cd",
+      "head_name": "cd_aux",
+      "level": "sample",
+      "epochs": 8
+    },
+    {
+      "name": "cd_aux",
+      "type": "head",
+      "input": "cd",
+      "train_with": "cd_fuse"
+    },
+    {
+      "name": "cd_fuse",
+      "type": "fusion",
+      "module": "hypertower_core.components.bridges.mono_bridge",
+      "class": "MonoBridge",
+      "inputs": [
+        "cd"
+      ],
+      "level": "sample",
+      "epochs": 10,
+      "train_towers": true,
+      "args": {
+        "use_ln": false
+      }
+    }
+  ],
+  "training": {
+    "lr": 0.001,
+    "batch_size": 32,
+    "tune_binary_threshold": true
+  },
+  "data_bundles": [
+    {
+      "file": "smoke.hdb",
+      "encrypted": false,
+      "mount": "data",
+      "unpacked_mb": 1,
+      "sha256": "b01dbf19fe3639a1b75fb80d75b31158f78dc42bec3767fe1caf94afd5b8fda5"
+    }
+  ],
+  "dataset": {
+    "n_samples": 400
+  }
+}