fix: execute sandboxed file ops inside containers (#4026)

Merged via /review-pr -> /prepare-pr -> /merge-pr.

Prepared head SHA: 795ec6aa2f
Co-authored-by: davidbors-snyk <240482518+davidbors-snyk@users.noreply.github.com>
Co-authored-by: steipete <58493+steipete@users.noreply.github.com>
Reviewed-by: @steipete

src/agents/sandbox/context.ts

@@ -9,6 +9,7 @@ import { DEFAULT_AGENT_WORKSPACE_DIR } from "../workspace.js";
 import { ensureSandboxBrowser } from "./browser.js";
 import { resolveSandboxConfigForAgent } from "./config.js";
 import { ensureSandboxContainer } from "./docker.js";
+import { createSandboxFsBridge } from "./fs-bridge.js";
 import { maybePruneSandboxes } from "./prune.js";
 import { resolveSandboxRuntimeStatus } from "./runtime-status.js";
 import { resolveSandboxScopeKey, resolveSandboxWorkspaceDir } from "./shared.js";
@@ -83,7 +84,7 @@ export async function resolveSandboxContext(params: {
     evaluateEnabled,
   });
 
-  return {
+  const sandboxContext: SandboxContext = {
     enabled: true,
     sessionKey: rawSessionKey,
     workspaceDir,
@@ -96,6 +97,10 @@ export async function resolveSandboxContext(params: {
     browserAllowHostControl: cfg.browser.allowHostControl,
     browser: browser ?? undefined,
   };
+
+  sandboxContext.fsBridge = createSandboxFsBridge({ sandbox: sandboxContext });
+
+  return sandboxContext;
 }
 
 export async function ensureSandboxWorkspaceForSession(params: {