feat: add direct sandbox workspace preview

[c121914yu]

What changed

• Add a read-only workspace preview server to fastgpt-ide-agent and expose it through agent-sandbox-proxy at /preview/{token}/{path}.
• Sign two-hour preview tickets in FastGPT, verify them through the existing backchannel, and resolve the matching sandbox endpoint without exposing upstream hosts to browsers.
• Support GET, HEAD, ETag, content length/type, and single byte ranges while rejecting traversal and symlinks escaping the workspace.
• Replace HTML preview and sandbox_get_file_url S3 uploads with direct workspace URLs so relative CSS, JavaScript, and image assets work.
• Keep existing WebSocket claims and keepalive behavior unchanged, using a separate Preview claim contract.
• Send proxy verification tickets through X-Sandbox-Ticket and keep preview content on the proxy origin.
• Require a dedicated HTTP(S) AGENT_SANDBOX_PREVIEW_PROXY_URL; optionally use an independent PREVIEW_PORT.

Why

The previous flow copied generated files to S3. This added storage work and broke multi-file previews because relative assets no longer resolved against the sandbox workspace.

The new flow treats the signed preview ticket as a two-hour, read-only workspace capability and streams files directly from the running sandbox.

Impact and rollout

• Preview links expire after two hours and grant read-only access to the ticket's workspace.
• Absolute asset paths such as /assets/app.js are unsupported; generated previews must use relative paths.
• Preview access refreshes sandbox activity when the proxy resolves the ticket; cached requests do not provide a persistent heartbeat.
• Default deployments keep WebSocket and Preview traffic on the existing single proxy port, but require separate ws(s):// and http(s):// URL settings. A second listener is enabled only by explicitly setting PREVIEW_PORT.
• FastGPT, agent-sandbox-proxy, and the sandbox runtime image must be deployed compatibly.
• Existing editor upload/download, WebSocket terminal/fs behavior, and workspace archive paths remain unchanged.

Validation

• Latest Service environment and Preview tests: 17 passed.
• App TypeScript typecheck passed.
• Rust CI passed fmt, clippy, and tests for both proxy and IDE Agent.
• Proxy release image built successfully for linux/arm64.
• Single-port compatibility and dual-port route isolation were verified against the local image.
• git diff --check

[github-actions]

Coverage Report

Status	Category	Percentage	Covered / Total
🔵	Lines	18.4%	1632 / 8868
🔵	Statements	18.39%	1713 / 9313
🔵	Functions	16.2%	342 / 2110
🔵	Branches	15.12%	761 / 5032

File Coverage

No changed files found.

Generated in workflow #1581 for commit 9d1122e by the Vitest Coverage Report Action

[github-actions]

✅ Admin Preview Image Ready!

ghcr.io/labring/fastgpt-pr:admin_9d1122e19e02f38e4f0f9e8e2fee0fe1dd7a6536

🕒 Time: 2026-07-20 22:18:02 (UTC+8)

[github-actions]

✅ Docs Preview Deployed!

🔗 👀 Click here to visit preview

ghcr.io/labring/fastgpt-docs-pr:cd498290d675add4928d4b3a2ed36f3cfdc85a6c

🕒 Time: 2026-07-16 16:27:22 (UTC+8)

[github-actions]

✅ Build Successful - Preview fastgpt Image for this PR:

ghcr.io/labring/fastgpt-pr:fastgpt_9d1122e19e02f38e4f0f9e8e2fee0fe1dd7a6536

🕒 Time: 2026-07-20 22:19:34 (UTC+8)

[Copilot]

Copilot was unable to review this pull request because the user who requested the review has reached their quota limit.