feat(runner): clone stage with ephemeral credential helper

Clone stage per tech spec §6, verbatim mechanics: every git invocation
carries a BLANK credential.helper first (suppresses OS keychain
helpers) then the inline veect helper; the PAT reaches git via child
env only — never argv, URLs, logs, or .git/config. GIT_TERMINAL_PROMPT
and GIT_ASKPASS are pinned so a headless clone can never hang on a TTY
or ambient IDE askpass. Staged status events (start/heartbeat/final) +
ready on success; named failures: invalid-git-url, auth-failed,
clone-failed (daemon's 'repository not exported' maps to bad-URL, not
auth). Integration suite clones the daemon-served vite-kitchen and an
authenticated dumb-HTTP remote that asserts the exact Basic credential
git presented, plus leak assertions over logs/argv/.git.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016j8z4VHjedXDTjEDNg7qHK

apps/runner/src/server.ts

@@ -8,7 +8,10 @@ import {
   type RunnerMessage,
   type RunnerStage,
 } from "@repo/core-runner-protocol";
+import { runCommand } from "./exec";
 import type { Logger } from "./log";
+import { cloneRepository } from "./stages/clone";
+import { runStage, type StageEmitter } from "./stages/stage-runner";
 
 /**
  * The runner's WS protocol server (ADR-027, protocol version "0").
@@ -137,38 +140,59 @@ export type CommandMessage = Extract<
   { type: "clone" | "install" | "scan" | "adapter-start" | "render-frame" }
 >;
 
-export interface StageEmitter {
-  status: (stage: RunnerStage, elapsedMs: number) => void;
-  error: (
-    cause: RunnerErrorCause,
-    message: string,
-    stage?: RunnerStage,
-  ) => void;
-}
-
 /** Stages that later walking-skeleton stories wire up (05+). */
 const NOT_IMPLEMENTED: Record<
-  CommandMessage["type"],
+  Exclude<CommandMessage["type"], "clone">,
   { cause: RunnerErrorCause; stage?: RunnerStage }
 > = {
-  clone: { cause: "clone-failed", stage: "cloning" },
   install: { cause: "install-failed", stage: "installing" },
   scan: { cause: "scan-failed", stage: "scanning" },
   "adapter-start": { cause: "adapter-start-failed", stage: "starting-preview" },
   "render-frame": { cause: "render-failed" },
 };
 
+interface CommandContext {
+  emit: StageEmitter;
+  /** Signal successful command completion — the session's idle marker. */
+  ready: () => void;
+  options: RunnerServerOptions;
+}
+
 async function handleCommand(
   command: CommandMessage,
-  emit: StageEmitter,
-  _options: RunnerServerOptions,
+  ctx: CommandContext,
 ): Promise<void> {
-  const notImplemented = NOT_IMPLEMENTED[command.type];
-  emit.error(
-    notImplemented.cause,
-    `the "${command.type}" command is not implemented by this runner build yet`,
-    notImplemented.stage,
-  );
+  const { emit, options } = ctx;
+  const stageOptions = {
+    emit,
+    heartbeatMs: options.heartbeatMs,
+    log: options.log,
+  };
+  switch (command.type) {
+    case "clone": {
+      const result = await runStage(
+        "cloning",
+        "clone-failed",
+        stageOptions,
+        () =>
+          cloneRepository({
+            workspaceDir: options.workspaceDir,
+            runCommand,
+            log: options.log,
+          })(command),
+      );
+      if (result.ok) ctx.ready();
+      return;
+    }
+    default: {
+      const notImplemented = NOT_IMPLEMENTED[command.type];
+      emit.error(
+        notImplemented.cause,
+        `the "${command.type}" command is not implemented by this runner build yet`,
+        notImplemented.stage,
+      );
+    }
+  }
 }
 
 function rawToString(data: RawData): string {
@@ -257,7 +281,11 @@ export async function startRunnerServer(
       log.info("command-received", { command: command.type });
       commandChain = commandChain.then(async () => {
         try {
-          await handleCommand(command, emit, options);
+          await handleCommand(command, {
+            emit,
+            ready: () => send({ type: "ready" }),
+            options,
+          });
         } catch (error) {
           // Stages map their own failures; this is the last-resort net.
           log.error("command-crashed", {