Add sandbox environment support (#4415)

## Thinking Path

> - Paperclip orchestrates AI agents for zero-human companies.
> - The environment/runtime layer decides where agent work executes and
how the control plane reaches those runtimes.
> - Today Paperclip can run locally and over SSH, but sandboxed
execution needs a first-class environment model instead of one-off
adapter behavior.
> - We also want sandbox providers to be pluggable so the core does not
hardcode every provider implementation.
> - This branch adds the Sandbox environment path, the provider
contract, and a deterministic fake provider plugin.
> - That required synchronized changes across shared contracts, plugin
SDK surfaces, server runtime orchestration, and the UI
environment/workspace flows.
> - The result is that sandbox execution becomes a core control-plane
capability while keeping provider implementations extensible and
testable.

## What Changed

- Added sandbox runtime support to the environment execution path,
including runtime URL discovery, sandbox execution targeting,
orchestration, and heartbeat integration.
- Added plugin-provider support for sandbox environments so providers
can be supplied via plugins instead of hardcoded server logic.
- Added the fake sandbox provider plugin with deterministic behavior
suitable for local and automated testing.
- Updated shared types, validators, plugin protocol definitions, and SDK
helpers to carry sandbox provider and workspace-runtime contracts across
package boundaries.
- Updated server routes and services so companies can create sandbox
environments, select them for work, and execute work through the sandbox
runtime path.
- Updated the UI environment and workspace surfaces to expose sandbox
environment configuration and selection.
- Added test coverage for sandbox runtime behavior, provider seams,
environment route guards, orchestration, and the fake provider plugin.

## Verification

- Ran locally before the final fixture-only scrub:
  - `pnpm -r typecheck`
  - `pnpm test:run`
  - `pnpm build`
- Ran locally after the final scrub amend:
  - `pnpm vitest run server/src/__tests__/runtime-api.test.ts`
- Reviewer spot checks:
  - create a sandbox environment backed by the fake provider plugin
  - run work through that environment
- confirm sandbox provider execution does not inherit host secrets
implicitly

## Risks

- This touches shared contracts, plugin SDK plumbing, server runtime
orchestration, and UI environment/workspace flows, so regressions would
likely show up as cross-layer mismatches rather than isolated type
errors.
- Runtime URL discovery and sandbox callback selection are sensitive to
host/bind configuration; if that logic is wrong, sandbox-backed
callbacks may fail even when execution succeeds.
- The fake provider plugin is intentionally deterministic and
test-oriented; future providers may expose capability gaps that this
branch does not yet cover.

## Model Used

- OpenAI Codex coding agent on a GPT-5-class backend in the
Paperclip/Codex harness. Exact backend model ID is not exposed
in-session. Tool-assisted workflow with shell execution, file editing,
git history inspection, and local test execution.

## Checklist

- [x] I have included a thinking path that traces from project context
to this change
- [x] I have specified the model used (with version and capability
details)
- [x] I have checked ROADMAP.md and confirmed this PR does not duplicate
planned core work
- [x] I have run tests locally and they pass
- [x] I have added or updated tests where applicable
- [ ] If this change affects the UI, I have included before/after
screenshots
- [x] I have updated relevant documentation to reflect my changes
- [x] I have considered and documented any risks above
- [x] I will address all Greptile and reviewer comments before
requesting merge

server/src/routes/issues.ts

@@ -39,10 +39,8 @@ import {
   accessService,
   agentService,
   executionWorkspaceService,
-  feedbackService,
   goalService,
   heartbeatService,
-  instanceSettingsService,
   issueApprovalService,
   issueThreadInteractionService,
   ISSUE_LIST_DEFAULT_LIMIT,
@@ -55,7 +53,6 @@ import {
   projectService,
   routineService,
   workProductService,
-  environmentService,
 } from "../services/index.js";
 import { logger } from "../middleware/logger.js";
 import { conflict, forbidden, HttpError, notFound, unauthorized } from "../errors.js";
@@ -73,11 +70,16 @@ import {
 } from "../attachment-types.js";
 import { queueIssueAssignmentWakeup } from "../services/issue-assignment-wakeup.js";
 import { assertEnvironmentSelectionForCompany } from "./environment-selection.js";
+import { executionWorkspaceService as executionWorkspaceServiceDirect } from "../services/execution-workspaces.js";
+import { feedbackService } from "../services/feedback.js";
+import { instanceSettingsService } from "../services/instance-settings.js";
+import { environmentService } from "../services/environments.js";
 import {
   applyIssueExecutionPolicyTransition,
   normalizeIssueExecutionPolicy,
   parseIssueExecutionState,
 } from "../services/issue-execution-policy.js";
+import type { PluginWorkerManager } from "../services/plugin-worker-manager.js";
 
 const MAX_ISSUE_COMMENT_LIMIT = 500;
 const updateIssueRouteSchema = updateIssueSchema.extend({
@@ -376,7 +378,7 @@ function buildExecutionStageWakeup(input: {
 export function issueRoutes(
   db: Db,
   storage: StorageService,
-  opts?: {
+  opts: {
     feedbackExportService?: {
       flushPendingFeedbackTraces(input?: {
         companyId?: string;
@@ -385,24 +387,30 @@ export function issueRoutes(
         now?: Date;
       }): Promise<unknown>;
     };
-  },
+    pluginWorkerManager?: PluginWorkerManager;
+  } = {},
 ) {
   const router = Router();
   const svc = issueService(db);
   const access = accessService(db);
-  const heartbeat = heartbeatService(db);
+  const heartbeat = heartbeatService(db, {
+    pluginWorkerManager: opts.pluginWorkerManager,
+  });
   const feedback = feedbackService(db);
   const instanceSettings = instanceSettingsService(db);
   const agentsSvc = agentService(db);
   const projectsSvc = projectService(db);
   const goalsSvc = goalService(db);
   const issueApprovalsSvc = issueApprovalService(db);
-  const executionWorkspacesSvc = executionWorkspaceService(db);
+  const executionWorkspacesSvc = executionWorkspaceServiceDirect(db);
   const workProductsSvc = workProductService(db);
   const documentsSvc = documentService(db);
   const issueReferencesSvc = issueReferenceService(db);
-  const routinesSvc = routineService(db);
+  const routinesSvc = routineService(db, {
+    pluginWorkerManager: opts.pluginWorkerManager,
+  });
   const feedbackExportService = opts?.feedbackExportService;
+  const environmentsSvc = environmentService(db);
   const upload = multer({
     storage: multer.memoryStorage(),
     limits: { fileSize: MAX_ATTACHMENT_BYTES, files: 1 },
@@ -425,10 +433,10 @@ export function issueRoutes(
   ) {
     if (environmentId === undefined || environmentId === null) return;
     await assertEnvironmentSelectionForCompany(
-      environmentService(db),
+      environmentsSvc,
       companyId,
       environmentId,
-      { allowedDrivers: ["local", "ssh"] },
+      { allowedDrivers: ["local", "ssh", "sandbox"] },
     );
   }