Add new regression and ensemble experiment configurations for V2-M and OrthoBridge

- Introduced multiple regression experiment configurations targeting vf_md, including:
  - cd_solo_reg_set.json: CD tower only regression setup.
  - img_solo_reg_set.json: Image tower only regression setup.
  - reg_head_epoch_sweep.json: Baseline regression sweeps at different epochs (50, 75, 100).
  - reg_head_set.json: Various regression setups including baseline and OrthoBridge configurations.
  - single_eye_reg.json: Single-eye regression setup for worst-eye aggregation analysis.

- Added ensemble configurations for OrthoBridge with different inner bridges:
  - ortho_alts_ensemble.json: Ensemble tests with ConcatBridge, PairwiseAdditiveBridge, and GatedAdditiveBridge.
  - ortho_alts_tritower.json: Tritower tests with the same inner bridges.

- Created V2-M specific configurations:
  - baseline_reg_nt50.json: Regression baseline with V2-M backbone.
  - geom_vec_gt.json and geom_vec_unet.json: Geometry vector injection experiments with V2-M.
  - single_l1_bridges.json: Single-eye ensemble experiments with various bridge types.
  - tritower_geom_gt.json: Tritower setup with GT contour-rasterized masks.

- Promoted existing experiments to higher repetitions for robustness.

v4/distributed/client.py

@@ -292,9 +292,17 @@ def _run_job(job: JobSpec, server: _Server,
     proc.wait()
     tailer.join(timeout=5)
     heartbeat.join(timeout=5)
-    log_file.unlink(missing_ok=True)
 
     success = proc.returncode == 0
+    if success:
+        log_file.unlink(missing_ok=True)
+    else:
+        failed_path = log_file.with_suffix(".failed.log")
+        try:
+            log_file.replace(failed_path)
+            print(f"[client] preserved failure log at {failed_path}", flush=True)
+        except Exception:
+            pass
 
     if not success:
         try: