ci: add cost-sensitive runner tiering (#4764)

* test persistent contabo runner poc

* test persistent runner web workspace poc

* test persistent runner local cache setup

* test persistent runner aggressive setup poc

* test persistent runner web postinstall profile

* test restore stable persistent runner poc

* test keep persistent runner web tests default

* test route persistent poc to zxiyun runner

* test relax web vitest timeout on persistent poc

* test harden web vitest cases for persistent runner

* test add runner perf probe

* test isolate runner perf probe dispatch

* test pin runner perf probe node

* test expand runner perf probe matrix

* ci: route heavy jobs through runner modes

* ci: keep web workspace tests on blacksmith

* test: update web runner mode assertion

* ci: route cost-sensitive runner tiers

* ci: move preflight to hosted runner

* ci: downshift blacksmith ui runners to 4vcpu

* test: fix file viewer timeout after merge

* ci: route e2e vitest to hosted default

* ci: centralize runner profile selection

* test: type runner profile assertions

* ci: route e2e vitest to default blacksmith

* ci: remove runner experiment probes

* test: restore postinstall guard coverage

Generated-By: looper 0.9.10+codex.autoclean (runner=fixer, agent=codex)

* test: cover postinstall script contract

* test: move postinstall guard to e2e

---------

Co-authored-by: Looper <looper@noreply.github.com>

.github/scripts/runners.py

@@ -0,0 +1,56 @@
+#!/usr/bin/env python3
+
+import json
+import os
+from pathlib import Path
+
+
+GITHUB_HOSTED = ["ubuntu-24.04"]
+CONTABO_CONTROL = ["self-hosted", "Linux", "X64", "od-persistent-ci", "od-ci-hot-poc"]
+BLACKSMITH_4V = ["blacksmith-4vcpu-ubuntu-2404"]
+
+
+def compact_json(value):
+    return json.dumps(value, separators=(",", ":"))
+
+
+def normalize_mode(raw_mode):
+    mode = (raw_mode or "default").strip().lower()
+    if mode in {"default", "performance", "economic"}:
+        return mode
+    return "default"
+
+
+def resolve_profiles(mode):
+    hosted_or_blacksmith = BLACKSMITH_4V if mode == "performance" else GITHUB_HOSTED
+    blacksmith_default = GITHUB_HOSTED if mode == "economic" else BLACKSMITH_4V
+    contabo_control = CONTABO_CONTROL if mode == "default" else GITHUB_HOSTED
+
+    return {
+        "mode": mode,
+        "github_hosted": GITHUB_HOSTED,
+        "contabo_control": contabo_control,
+        "hosted_or_blacksmith": hosted_or_blacksmith,
+        "blacksmith_default": blacksmith_default,
+    }
+
+
+def main():
+    profiles = resolve_profiles(normalize_mode(os.environ.get("OD_CI_RUNNER_MODE")))
+    output_path = os.environ.get("GITHUB_OUTPUT")
+    lines = [
+        f"{key}={value if isinstance(value, str) else compact_json(value)}"
+        for key, value in profiles.items()
+    ]
+
+    if output_path:
+        with Path(output_path).open("a", encoding="utf-8") as output:
+            for line in lines:
+                output.write(f"{line}\n")
+    else:
+        for line in lines:
+            print(line)
+
+
+if __name__ == "__main__":
+    main()