Lift drill into evals/ at 013fcb8b7dbefd6d3fa4653493e5d2ec8e7f985b

rsync of obra/drill@013fcb8b7d into superpowers/evals/, excluding
.git/, .venv/, results/, .env/, __pycache__/, *.egg-info/,
.private-journal/.

The drill repo is unaffected by this commit; archival is a separate
manual step after this PR merges.

Source SHA recorded at evals/.drill-source-sha for divergence
detection.

evals/drill/backend.py

@@ -0,0 +1,111 @@
+"""Backend config loader and command builder."""
+
+from __future__ import annotations
+
+import os
+import re
+from dataclasses import dataclass
+from pathlib import Path
+from typing import Any
+
+import yaml
+
+
+@dataclass
+class Backend:
+    name: str
+    cli: str
+    args: list[str]
+    required_env: list[str]
+    hooks: dict[str, list[str]]
+    shutdown: str
+    idle: dict[str, Any]
+    startup_timeout: int
+    terminal: dict[str, int]
+    session_logs: dict[str, str]
+    turn_timeout: int | None = None
+    busy_pattern: str = ""
+    max_busy_seconds: int = 1800
+
+    def build_command(self, workdir: str) -> list[str]:
+        resolved = [_interpolate_env(arg) for arg in self.args]
+        return [self.cli, *resolved]
+
+    def validate_env(self) -> None:
+        missing = [v for v in self.required_env if not os.environ.get(v)]
+        if missing:
+            raise OSError(
+                f"Missing required environment variables for {self.name} backend: "
+                + ", ".join(missing)
+            )
+
+    def is_ready_line(self, line: str) -> bool:
+        pattern = self.idle.get("ready_pattern", "")
+        return bool(re.search(pattern, line))
+
+    def is_busy_line(self, line: str) -> bool:
+        if not self.busy_pattern:
+            return False
+        return bool(re.search(self.busy_pattern, line))
+
+    @property
+    def quiescence_seconds(self) -> float:
+        return self.idle.get("quiescence_seconds", 5)
+
+    @property
+    def cols(self) -> int:
+        return self.terminal.get("cols", 200)
+
+    @property
+    def rows(self) -> int:
+        return self.terminal.get("rows", 50)
+
+    @property
+    def model(self) -> str | None:
+        """Model name from args (looks for --model or -m flag)."""
+        for i, arg in enumerate(self.args):
+            if arg in ("--model", "-m") and i + 1 < len(self.args):
+                return self.args[i + 1]
+        return None
+
+    @property
+    def family(self) -> str:
+        """Normalize backend name to a family for log-dir / normalizer dispatch."""
+        for fam in ("claude", "codex", "gemini"):
+            if self.name == fam or self.name.startswith(f"{fam}-"):
+                return fam
+        return "other"
+
+
+def load_backend(name: str, backends_dir: Path) -> Backend:
+    path = backends_dir / f"{name}.yaml"
+    if not path.exists():
+        raise FileNotFoundError(f"Backend config not found: {path}")
+    with open(path) as f:
+        data = yaml.safe_load(f)
+    return Backend(
+        name=data["name"],
+        cli=data["cli"],
+        args=data.get("args", []),
+        required_env=data.get("required_env", []),
+        hooks=data.get("hooks", {"pre_run": [], "post_run": []}),
+        shutdown=data.get("shutdown", "/exit"),
+        idle=data.get("idle", {}),
+        startup_timeout=data.get("startup_timeout", 30),
+        terminal=data.get("terminal", {"cols": 200, "rows": 50}),
+        session_logs=data.get("session_logs", {}),
+        turn_timeout=data.get("turn_timeout"),
+        busy_pattern=data.get("busy_pattern", ""),
+        max_busy_seconds=data.get("max_busy_seconds", 1800),
+    )
+
+
+def _interpolate_env(value: str) -> str:
+    def replacer(match: re.Match[str]) -> str:
+        var = match.group(1)
+        val = os.environ.get(var)
+        if val is None:
+            raise OSError(f"Environment variable {var} not set")
+        return val
+
+    return re.sub(r"\$\{(\w+)\}", replacer, value)