Add multi_nimlibp2p_kad: kad-dht regression matrix (version x muxer)

Sequential kad-dht regression sweep across nim-libp2p versions and muxers,
env-configurable via REGRESSION_* (smoke / single-version / full matrix). Each
version x muxer combination is one full NimLibp2pExperiment run via Multiple.

Rebased onto master from the stale alan/regression-campaign branch (20 commits
behind). This runner was the only piece still unique to that branch -- the
kad-dht mesh formation, publisher provisioning, and num_relay_nodes rename it
was built on have since landed on master independently. Passes num_relay_nodes
(not the old num_nodes key) and drops the add_parser override that master's
BaseExperiment now forbids.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: radiken

src/deployments/experiments/libp2p/multi_nimlibp2p_kad.py

@@ -0,0 +1,75 @@
+import os
+from typing import Iterable, List, Optional
+
+from src.deployments.core.configs.container import Image
+from src.deployments.experiments.libp2p.nimlibp2p import NimLibp2pExperiment
+from src.deployments.experiments.multi_experiment import Multiple
+from src.deployments.registry import experiment
+
+# nim-libp2p regression matrix: each version x muxer is one full kad-dht run.
+# The sweep is env-configurable so the same experiment drives a smoke test, a
+# single-version pass (runs are sequential to keep measurements clean), or the
+# full matrix -- see REGRESSION_* below.
+IMAGES = {
+    "2.0.0": Image(repo="radiken/dst-test-node-regression", tag="v2.0.0-kad"),
+    "2.1.0": Image(repo="radiken/dst-test-node-regression", tag="v2.1.0-kad"),
+}
+
+
+def _env_list(name: str, default: str) -> list:
+    return [x.strip() for x in os.environ.get(name, default).split(",") if x.strip()]
+
+
+VERSIONS = _env_list("REGRESSION_VERSIONS", "2.1.0,2.0.0")
+MUXERS = _env_list("REGRESSION_MUXERS", "mplex,yamux,quic")
+MESSAGE_SIZES = [int(x) for x in _env_list("REGRESSION_SIZES", "1000")]
+NUM_NODES = int(os.environ.get("REGRESSION_NUM_NODES", "1000"))
+NUM_MESSAGES = int(os.environ.get("REGRESSION_NUM_MESSAGES", "600"))
+# delay_cold_start is how long we wait after the nodes are deployed (their start
+# delay + kad-dht mesh formation) before the publisher fires; shorten it via the
+# env var for small smoke runs.
+COLD_START = int(os.environ.get("REGRESSION_COLD_START", str(7 * 60)))
+
+
+@experiment(name="multi_nimlibp2p_kad")
+class MultiNimlibp2pKad(Multiple):
+    """nim-libp2p regression sweep: kad-dht, version x muxer."""
+
+    def model_post_init(self, __context) -> None:
+        self.config.name = NimLibp2pExperiment.name
+        super().model_post_init(__context)
+
+    def get_params_paths(self) -> Optional[dict]:
+        return None
+
+    def exp_params(self) -> Iterable[dict]:
+        base = {
+            "discovery": "kad-dht",
+            "bootstrap_nodes": 1,
+            "num_relay_nodes": NUM_NODES,
+            "num_messages": NUM_MESSAGES,
+            "delay_after_publish": 1,  # 1 msg/s
+            "delay_cold_start": COLD_START,
+            "node_start_delay": 5 * 60,
+        }
+        for version in VERSIONS:
+            for size in MESSAGE_SIZES:
+                for muxer in MUXERS:
+                    yield {
+                        **base,
+                        "image": IMAGES[version],
+                        "version": version,
+                        "muxer": muxer,
+                        "message_size_bytes": size,
+                    }
+
+    def get_params_list(self) -> List[dict]:
+        return list(self.exp_params())
+
+    def get_name_from_params(self, params: dict) -> str:
+        return (
+            f"version_{params['version']}"
+            f"__muxer_{params['muxer']}"
+            f"__size_{params['message_size_bytes']}"
+            f"__nodes_{params['num_relay_nodes']}"
+        )