Quote variable values with spaces in the displayed run command line

Values containing spaces (e.g. an env-passed SCENE="Glitz and glam")
rendered as bare, space-separated words in the run detail view,
indistinguishable from separate argv/env entries. Now anything outside
a safe bareword character set is quoted and escaped for display only -
actual execution is unaffected, since values are always passed as
discrete argv elements/env vars, never through a shell.

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

src/lib/runner/build-args.ts

@@ -18,6 +18,15 @@ function stringifyValue(value: unknown, joinWith: string): string {
   return String(value);
 }
 
+/** Quotes a value for the human-readable `redactedCommandLine` display only - the real
+ * invocation always passes values as discrete argv elements/env vars (see build note below),
+ * so this never affects execution. Without it, a value like "Glitz and glam" renders as three
+ * bare words indistinguishable from separate argv entries. */
+function quoteForDisplay(value: string): string {
+  if (value !== "" && /^[a-zA-Z0-9_@%+=:,./-]+$/.test(value)) return value;
+  return `"${value.replace(/([$`"\\])/g, "\\$1")}"`;
+}
+
 /** Builds an argv-array invocation from validated variable values. Never produces a shell string. */
 export function buildInvocation(
   script: ScriptConfig,
@@ -43,7 +52,10 @@ export function buildInvocation(
         const argName = variable.argName!;
         const value = stringifyValue(raw, variable.joinWith);
         argv.push(argName, value);
-        redactedArgv.push(argName, variable.secret ? REDACTED : value);
+        redactedArgv.push(
+          argName,
+          variable.secret ? REDACTED : quoteForDisplay(value),
+        );
         break;
       }
       case "flag": {
@@ -57,7 +69,7 @@ export function buildInvocation(
         const value = stringifyValue(raw, variable.joinWith);
         env[variable.envName!] = value;
         redactedEnvAssignments.push(
-          `${variable.envName}=${variable.secret ? REDACTED : value}`,
+          `${variable.envName}=${variable.secret ? REDACTED : quoteForDisplay(value)}`,
         );
         break;
       }