Add per-job GPU support via workflow labels

Parse gpu:T4/gpu:A100/etc from job labels and pass to
modal.Sandbox.create(). Supports T4, L4, A100, A100-80GB, H100.
GPU defaults to None (CPU-only) if no gpu: label is present.

Author: manascb1344

app.py

@@ -93,6 +93,14 @@ def format(self, record: logging.LogRecord) -> str:
     if MAX_CONCURRENT_PER_REPO <= 0:
         MAX_CONCURRENT_PER_REPO = None
 
+GPU_MAP = {
+    "t4": modal.gpu.T4(),
+    "l4": modal.gpu.L4(),
+    "a100": modal.gpu.A100(),
+    "a100-80gb": modal.gpu.A100_80GB(),
+    "h100": modal.gpu.H100(),
+}
+
 # =============================================================================
 # TRUST MODEL
 # =============================================================================
@@ -476,6 +484,23 @@ async def github_webhook(request: Request):
         )
         return {"status": "ignored", "reason": "no modal label"}
 
+    gpu_config = None
+    for label in job_labels:
+        if label.startswith("gpu:"):
+            gpu_key = label.split(":", 1)[1].lower()
+            gpu_config = GPU_MAP.get(gpu_key)
+            if not gpu_config:
+                logger.warning(
+                    "Unknown GPU type requested",
+                    extra={"job_id": job_id, "gpu": gpu_key},
+                )
+            else:
+                logger.info(
+                    "GPU requested for job",
+                    extra={"job_id": job_id, "gpu": gpu_key},
+                )
+            break
+
     # Repository allowlist validation
     if ALLOWED_REPOS and repo_full_name not in ALLOWED_REPOS:
         logger.warning(
@@ -618,7 +643,7 @@ async def github_webhook(request: Request):
                 )
                 raise HTTPException(status_code=500, detail="Internal server error")
 
-        logger.info("Spawning sandbox", extra={"job_id": job_id, "repo": repo_full_name})
+        logger.info("Spawning sandbox", extra={"job_id": job_id, "repo": repo_full_name, "gpu": gpu_config is not None})
 
         cmd = (
             "bash -c '/start-dockerd.sh &'"
@@ -637,6 +662,7 @@ async def github_webhook(request: Request):
             app=app,
             timeout=TIMEOUT_SECONDS,
             env={"GHA_JIT_CONFIG": jit_config},
+            gpu=gpu_config,
             experimental_options={"enable_docker": True},
         )