Add Novita sandbox provider plugin (#7595)

## Thinking Path

> - Paperclip is the open source app people use to manage AI agents for
work.
> - Paperclip already separates agent adapters from execution
environments, so agents can run locally, over SSH, or through sandbox
providers.
> - Sandbox provider plugins let Paperclip add new cloud runtimes
without changing each agent adapter.
> - Novita Agent Sandbox is a cloud runtime for AI agent workloads with
isolated filesystems, command execution, templates, timeout controls,
and pause/resume behavior.
> - Paperclip currently has sandbox provider examples for Daytona and
Cloudflare, but not Novita.
> - This pull request adds a Novita sandbox provider plugin using the
existing provider-plugin lifecycle.
> - The benefit is that Paperclip users can run existing adapters such
as Codex, Claude, Gemini, OpenCode, Cursor, or ACPX inside Novita Agent
Sandbox environments.

## Linked Issues or Issue Description

Fixes #7596

## What Changed

- Added `packages/plugins/sandbox-providers/novita` as a standalone
sandbox provider plugin package.
- Registered provider key `novita` with `kind: "sandbox_provider"` and
`environment.drivers.register` capability.
- Implemented Novita environment lifecycle hooks: validate config,
probe, acquire lease, resume lease, release lease, destroy lease,
realize workspace, and execute commands.
- Added config support for `apiKey`, `domain`, `template`,
`requestedCwd`, `timeoutMs`, `requestTimeoutMs`, `secure`, `autoPause`,
and `reuseLease`.
- Added README documentation for setup, configuration, and lifecycle
behavior.
- Added tests for manifest shape, config parsing, safe shell command
wrapping, stdin delimiter safety, and env-key validation.

## Verification

From `packages/plugins/sandbox-providers/novita`:

- `pnpm typecheck`
- `pnpm test`

The tests avoid live Novita API calls and cover the provider's static
contract and command-wrapping behavior. Live end-to-end verification
requires a Paperclip instance with the plugin installed and a Novita API
key configured as either a Paperclip secret or `NOVITA_API_KEY` in the
worker environment.

## Risks

- This adds a new direct dependency on the Novita Sandbox JS SDK
(`novita-sandbox`). Socket/Snyk should review the package as part of
normal dependency checks.
- The implementation relies on Novita SDK command execution semantics;
live provider behavior should be verified with a real Novita sandbox
before marking the plugin production-ready.
- `reuseLease` maps Paperclip release behavior to Novita `betaPause()`.
If pause is unavailable for a selected template, the plugin falls back
to best-effort kill during release.
- Low migration risk for existing users because this is a new standalone
provider plugin and does not change existing adapters or built-in
providers.

> For core feature work, check [`ROADMAP.md`](ROADMAP.md) first and
discuss it in `#dev` before opening the PR. Feature PRs that overlap
with planned core work may need to be redirected — check the roadmap
first. See `CONTRIBUTING.md`.

## Model Used

OpenAI GPT-5 Codex via Codex CLI, with repository file access, shell
command execution, GitHub CLI/API usage, and local TypeScript/Vitest
verification. Web and local documentation context were used for Novita
Sandbox SDK/API behavior.

## 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 searched GitHub for duplicate or related PRs and linked
them above
- [x] I have either (a) linked existing issues with `Fixes: #` / `Closes
#` / `Refs #` OR (b) described the issue in-PR following the relevant
issue template
- [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
- [ ] All Paperclip CI gates are green
- [ ] Greptile is 5/5 with no open P2s, recommendations, or follow-ups
- [x] I will address all Greptile and reviewer comments before
requesting merge

---------

Co-authored-by: Paperclip <noreply@paperclip.ing>
Co-authored-by: Devin Foley <devin@paperclip.ing>

scripts/link-plugin-dev-sdk.mjs

@@ -1,6 +1,6 @@
 #!/usr/bin/env node
 
-import { existsSync, mkdirSync, lstatSync, rmSync, symlinkSync } from "node:fs";
+import { existsSync, mkdirSync, lstatSync, readlinkSync, rmSync, symlinkSync } from "node:fs";
 import { dirname, join, relative, resolve } from "node:path";
 import { fileURLToPath } from "node:url";
 
@@ -20,6 +20,12 @@ mkdirSync(scopeDir, { recursive: true });
 try {
   const stat = lstatSync(linkTarget);
   if (stat.isSymbolicLink()) {
+    const existingTarget = readlinkSync(linkTarget);
+    const relativeSdkDir = relative(scopeDir, sdkDir);
+    if (existingTarget === relativeSdkDir) {
+      console.log(`  ✓ Local @paperclipai/plugin-sdk already linked for ${packageDir}`);
+      process.exit(0);
+    }
     rmSync(linkTarget, { force: true });
   } else {
     console.log("  i Keeping existing installed @paperclipai/plugin-sdk directory in place");

scripts/release-package-manifest.json

@@ -134,6 +134,11 @@
     "name": "@paperclipai/plugin-kubernetes",
     "publishFromCi": false
   },
+  {
+    "dir": "packages/plugins/sandbox-providers/novita",
+    "name": "@paperclipai/plugin-novita-sandbox",
+    "publishFromCi": false
+  },
   {
     "dir": "ui",
     "name": "@paperclipai/ui",