docs: add Antigravity IDE integration documentation (#22177)

Closes #21130

Adds documentation for Google Antigravity IDE integration, following the
same pattern as Cursor and Windsurf (dedicated page for desktop IDEs).

**Changes:**

- `docs/user-guides/workspace-access/antigravity.md` — New dedicated
page with install guide, Coder extension setup, and template
configuration example using the [Antigravity registry
module](https://registry.coder.com/modules/coder/antigravity)
- `docs/user-guides/workspace-access/index.md` — Added Antigravity IDE
section alongside Cursor and Windsurf
- `docs/manifest.json` — Added sidebar navigation entry after Windsurf

Antigravity uses the `antigravity://` protocol (added in #20873) and the
built-in `/icon/antigravity.svg` icon (added in #21068). The [registry
module](https://registry.coder.com/modules/coder/antigravity) wraps
`vscode-desktop-core` with `protocol = "antigravity"`.

Created on behalf of @matifali

Co-authored-by: blink-so[bot] <211532188+blink-so[bot]@users.noreply.github.com>

docs/manifest.json

@@ -293,6 +293,11 @@
 							"title": "Windsurf",
 							"description": "Access your workspace with Windsurf",
 							"path": "./user-guides/workspace-access/windsurf.md"
+						},
+						{
+							"title": "Antigravity",
+							"description": "Access your workspace with Antigravity",
+							"path": "./user-guides/workspace-access/antigravity.md"
 						}
 					]
 				},

docs/user-guides/workspace-access/antigravity.md

@@ -0,0 +1,68 @@
+# Antigravity
+
+[Antigravity](https://antigravity.google/) is Google's desktop IDE.
+
+Follow this guide to use Antigravity to access your Coder workspaces.
+
+If your team uses Antigravity regularly, ask your Coder administrator to add Antigravity as a workspace application in your template.
+You can also use the [Antigravity module](https://registry.coder.com/modules/coder/antigravity) to easily add Antigravity to your Coder templates.
+
+## Install Antigravity
+
+Antigravity connects to your Coder workspaces using the Coder extension:
+
+1. [Install Antigravity](https://antigravity.google/) on your local machine.
+
+1. Open Antigravity and sign in with your Google account.
+
+## Install the Coder extension
+
+1. You can install the Coder extension through the Marketplace built in to Antigravity or manually.
+
+   <div class="tabs">
+
+   ## Extension Marketplace
+
+   Search for Coder from the Extensions Pane and select **Install**.
+
+   ## Manually
+
+   1. Download the [latest vscode-coder extension](https://github.com/coder/vscode-coder/releases/latest) `.vsix` file.
+
+   1. Drag the `.vsix` file into the extensions pane of Antigravity.
+
+      Alternatively:
+
+      1. Open the Command Palette
+         (<kdb>Ctrl</kdb>+<kdb>Shift</kdb>+<kdb>P</kdb> or <kdb>Cmd</kdb>+<kdb>Shift</kdb>+<kdb>P</kdb>) and search for `vsix`.
+
+      1. Select **Extensions: Install from VSIX** and select the vscode-coder extension you downloaded.
+
+   </div>
+
+## Open a workspace in Antigravity
+
+1. From the Antigravity Command Palette (<kdb>Ctrl</kdb>+<kdb>Shift</kdb>+<kdb>P</kdb> or <kdb>Cmd</kdb>+<kdb>Shift</kdb>+<kdb>P</kdb>),
+   enter `coder` and select **Coder: Login**.
+
+1. Follow the prompts to login and copy your session token.
+
+   Paste the session token in the **Coder API Key** dialogue in Antigravity.
+
+1. Antigravity prompts you to open a workspace, or you can use the Command Palette to run **Coder: Open Workspace**.
+
+## Template configuration
+
+Your Coder administrator can add Antigravity as a one-click workspace app using
+the [Antigravity module](https://registry.coder.com/modules/coder/antigravity)
+from the Coder registry:
+
+```tf
+module "antigravity" {
+  count    = data.coder_workspace.me.start_count
+  source   = "registry.coder.com/coder/antigravity/coder"
+  version  = "1.0.0"
+  agent_id = coder_agent.example.id
+  folder   = "/home/coder/project"
+}
+```

docs/user-guides/workspace-access/index.md

@@ -102,6 +102,13 @@ Read more about [using Cursor with your workspace](./cursor.md).
 [Windsurf](./windsurf.md) is Codeium's code editor designed for AI-assisted development.
 Windsurf connects using the Coder extension.
 
+## Antigravity
+
+[Antigravity](https://antigravity.google/) is Google's desktop IDE.
+Antigravity connects using the Coder extension.
+
+Read more about [using Antigravity with your workspace](./antigravity.md).
+
 ## JetBrains IDEs
 
 We support JetBrains IDEs using