Add SSH environment support (#4358)

## Thinking Path

> - Paperclip orchestrates AI agents for zero-human companies
> - The environments subsystem already models execution environments,
but before this branch there was no end-to-end SSH-backed runtime path
for agents to actually run work against a remote box
> - That meant agents could be configured around environment concepts
without a reliable way to execute adapter sessions remotely, sync
workspace state, and preserve run context across supported adapters
> - We also need environment selection to participate in normal
Paperclip control-plane behavior: agent defaults, project/issue
selection, route validation, and environment probing
> - Because this capability is still experimental, the UI surface should
be easy to hide and easy to remove later without undoing the underlying
implementation
> - This pull request adds SSH environment execution support across the
runtime, adapters, routes, schema, and tests, then puts the visible
environment-management UI behind an experimental flag
> - The benefit is that we can validate real SSH-backed agent execution
now while keeping the user-facing controls safely gated until the
feature is ready to come out of experimentation

## What Changed

- Added SSH-backed execution target support in the shared adapter
runtime, including remote workspace preparation, skill/runtime asset
sync, remote session handling, and workspace restore behavior after
runs.
- Added SSH execution coverage for supported local adapters, plus remote
execution tests across Claude, Codex, Cursor, Gemini, OpenCode, and Pi.
- Added environment selection and environment-management backend support
needed for SSH execution, including route/service work, validation,
probing, and agent default environment persistence.
- Added CLI support for SSH environment lab verification and updated
related docs/tests.
- Added the `enableEnvironments` experimental flag and gated the
environment UI behind it on company settings, agent configuration, and
project configuration surfaces.

## Verification

- `pnpm exec vitest run
packages/adapters/claude-local/src/server/execute.remote.test.ts
packages/adapters/cursor-local/src/server/execute.remote.test.ts
packages/adapters/gemini-local/src/server/execute.remote.test.ts
packages/adapters/opencode-local/src/server/execute.remote.test.ts
packages/adapters/pi-local/src/server/execute.remote.test.ts`
- `pnpm exec vitest run server/src/__tests__/environment-routes.test.ts`
- `pnpm exec vitest run
server/src/__tests__/instance-settings-routes.test.ts`
- `pnpm exec vitest run ui/src/lib/new-agent-hire-payload.test.ts
ui/src/lib/new-agent-runtime-config.test.ts`
- `pnpm -r typecheck`
- `pnpm build`
- Manual verification on a branch-local dev server:
  - enabled the experimental flag
  - created an SSH environment
  - created a Linux Claude agent using that environment
- confirmed a run executed on the Linux box and synced workspace changes
back

## Risks

- Medium: this touches runtime execution flow across multiple adapters,
so regressions would likely show up in remote session setup, workspace
sync, or environment selection precedence.
- The UI flag reduces exposure, but the underlying runtime and route
changes are still substantial and rely on migration correctness.
- The change set is broad across adapters, control-plane services,
migrations, and UI gating, so review should pay close attention to
environment-selection precedence and remote workspace lifecycle
behavior.

## Model Used

- OpenAI Codex via Paperclip's local Codex adapter, GPT-5-class coding
model with tool use and code execution in the local repo workspace. The
local adapter does not surface a more specific public model version
string in this branch workflow.

## 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/app.ts

@@ -17,6 +17,7 @@ import { projectRoutes } from "./routes/projects.js";
 import { issueRoutes } from "./routes/issues.js";
 import { issueTreeControlRoutes } from "./routes/issue-tree-control.js";
 import { routineRoutes } from "./routes/routines.js";
+import { environmentRoutes } from "./routes/environments.js";
 import { executionWorkspaceRoutes } from "./routes/execution-workspaces.js";
 import { goalRoutes } from "./routes/goals.js";
 import { approvalRoutes } from "./routes/approvals.js";
@@ -43,7 +44,7 @@ import { pluginUiStaticRoutes } from "./routes/plugin-ui-static.js";
 import { applyUiBranding } from "./ui-branding.js";
 import { logger } from "./middleware/logger.js";
 import { DEFAULT_LOCAL_PLUGIN_DIR, pluginLoader } from "./services/plugin-loader.js";
-import { createPluginWorkerManager } from "./services/plugin-worker-manager.js";
+import { createPluginWorkerManager, type PluginWorkerManager } from "./services/plugin-worker-manager.js";
 import { createPluginJobScheduler } from "./services/plugin-job-scheduler.js";
 import { pluginJobStore } from "./services/plugin-job-store.js";
 import { createPluginToolDispatcher } from "./services/plugin-tool-dispatcher.js";
@@ -129,6 +130,7 @@ export async function createApp(
     hostVersion?: string;
     localPluginDir?: string;
     pluginMigrationDb?: Db;
+    pluginWorkerManager?: PluginWorkerManager;
     betterAuthHandler?: express.RequestHandler;
     resolveSession?: (req: ExpressRequest) => Promise<BetterAuthSessionResult | null>;
   },
@@ -170,6 +172,9 @@ export async function createApp(
   }
   app.use(llmRoutes(db));
 
+  const hostServicesDisposers = new Map<string, () => void>();
+  const workerManager = opts.pluginWorkerManager ?? createPluginWorkerManager();
+
   // Mount API routes
   const api = Router();
   api.use(boardMutationGuard());
@@ -192,6 +197,7 @@ export async function createApp(
   }));
   api.use(issueTreeControlRoutes(db));
   api.use(routineRoutes(db));
+  api.use(environmentRoutes(db));
   api.use(executionWorkspaceRoutes(db));
   api.use(goalRoutes(db));
   api.use(approvalRoutes(db));
@@ -207,8 +213,6 @@ export async function createApp(
   if (opts.databaseBackupService) {
     api.use(instanceDatabaseBackupRoutes(opts.databaseBackupService));
   }
-  const hostServicesDisposers = new Map<string, () => void>();
-  const workerManager = createPluginWorkerManager();
   const pluginRegistry = pluginRegistryService(db);
   const eventBus = createPluginEventBus();
   setPluginEventBus(eventBus);