fix(sandbox): evidence-gate runner failures (round 1)

packages/bash/bash-sandbox/src/helpers.ts

@@ -5,6 +5,13 @@
  */
 
 import type { BashRunResult } from '@deepseek-ai/dsh-bash'
+import type { RunnerFailureRule } from '@deepseek-ai/dsh-sandbox'
+
+/** Fatal runner evidence retained for infrastructure-error detail. */
+interface RunnerFailureMatch {
+  /** The original stderr line that matched a fatal signature. */
+  detail: string
+}
 
 /**
  * Quote one string as a single-quoted POSIX shell word.
@@ -26,13 +33,33 @@ export function classifyDenial(result: BashRunResult, signatures: readonly strin
 }
 
 /**
- * Classify a failed run against the selected backend's runner-failure dialect.
- * @param result - settled foreground run.
- * @param signatures - case-insensitive runner-failure substrings from the active wrap.
- * @returns whether the failed run matches that runner-failure dialect.
+ * Classify one settled process against the selected backend's structured
+ * runner-failure rules. Each rule requires a nonzero exit, its optional
+ * exit-code gate, and a fatal signature on one stderr line after exact
+ * informational lines are excluded.
+ * @param exitCode - process exit code; null means signal termination.
+ * @param stderr - collected stderr text, left unchanged.
+ * @param rules - structured runner-failure rules from the active wrap.
+ * @returns the first matching fatal line, or undefined when evidence is insufficient.
  */
-export function classifyRunnerFailure(result: BashRunResult, signatures: readonly string[]): boolean {
-  return matchesSignature(result.exitCode, result.stderr.text, signatures)
+export function classifyRunnerFailure(
+  exitCode: number | null,
+  stderr: string,
+  rules: readonly RunnerFailureRule[],
+): RunnerFailureMatch | undefined {
+  if (exitCode === null || exitCode === 0) return undefined
+  const lines = stderr.split(/\r?\n/)
+  for (const rule of rules) {
+    if (rule.allowedExitCodes !== undefined && !rule.allowedExitCodes.includes(exitCode)) continue
+    const informationalLines = new Set((rule.informationalLines ?? []).map(line => line.toLowerCase()))
+    const fatalSignatures = rule.fatalSignatures.map(signature => signature.toLowerCase())
+    for (const line of lines) {
+      const lowered = line.toLowerCase()
+      if (informationalLines.has(lowered)) continue
+      if (fatalSignatures.some(signature => lowered.includes(signature))) return { detail: line }
+    }
+  }
+  return undefined
 }
 
 /**