poc: tangent projects

[maxy-shpfy]

Description

Introduces the Tangent Shell workspace — a beta-flagged area where users collaborate with Tangent agents to build, improve, and debug ML pipelines. The feature is gated behind a new tangent-shell feature flag and adds a full project management experience including:

• A projects listing page (/tangent) with a prompt composer to create new projects and a grid of existing ones.
• A project workspace page (/tangent/$projectId) with a docked sidebar (Sessions, Agents, Assets, Project Resources), a tabbed chat pane, and a resizable Dynamic Workarea that hosts embedded pipeline editors and artifact viewers side-by-side.
• Per-tab embedded pipeline editors (EmbeddedPipelineEditor) that each host their own remote-env agent, allowing Tangent to drive multiple open pipelines simultaneously.
• A project-level agent (TangentProjectAgentProvider) that registers workarea RPC tools (open_pipeline, list_workarea_tabs, close_workarea_tab) and a routing bridge that forwards editor commands to whichever pipeline tab is active.
• Local-first persistence via a new Dexie database (tangentStorage) storing projects, sessions, resources, and a backlog.
• A useTangentSettings hook that moves the Tangent base URL from a build-time env var (VITE_TANGENT_BASE_URL) into localStorage, letting users point tangle-ui at any Tangent origin without rebuilding. A corresponding settings UI is added to Agent Settings.
• A custom TangentEmbedProvider that replaces the upstream TangentProvider, applying socket config synchronously so Socket.IO reads the correct origin before chat elements subscribe. It also handles mounted-prefix base URLs (e.g. /tangent) by splitting them into socketUrl + socketPath.
• Shared utilities extracted to src/routes/v2/shared/tangent/: CloseableTabTrigger, TangentChatPane, useTangentSessionTabs, socketConfig, and constants.
• @tangent/embed-react, @tangent/remote-subagent, and @tangent/shared dependencies switched from local file: paths to pinned GitHub tarball references.

Related Issue and Pull requests

Type of Change

• Bug fix
• New feature
• Improvement
• Cleanup/Refactor
• Breaking change
• Documentation update

Checklist

• I have tested this does not break current pipelines / runs functionality
• I have tested the changes on staging

Screenshots (if applicable)

Test Instructions

1. Enable the tangent-shell beta flag in Settings → Feature Flags.
2. Confirm a Tangent Shell entry with an "AI" badge appears in the sidebar.
3. Navigate to /tangent and create a project using the prompt composer.
4. Inside the project workspace, start a session and verify the chat pane connects to the configured Tangent origin.
5. Use the Resources panel to attach a pipeline or run; confirm it appears in the Dynamic Workarea when opened.
6. In Settings → Agent Settings, change the Tangent base URL, save, and verify the chat and remote-env connections use the new origin without a page reload.
7. Reset the URL and confirm it reverts to http://localhost:5173.
8. Verify that the existing editor Tangent chat window (when tangent-embed-chat is enabled) still works and is unaffected by the new workspace.

Additional Comments

The VITE_TANGENT_BASE_URL build-time constant has been removed. Any deployment that previously set this env var must instead configure the URL via the new Agent Settings UI or localStorage key tangle.tangent.config.

[github-actions]

🎩 Preview

A preview build has been created at: 08-19-poc_tangent_projects/1669edd

[maxy-shpfy]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• poc: tangent projects #2660 👈 (View in Graphite)
• poc: tangent embed ui #2659
• master

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