feat: add tooltip field to workspace app that renders as markdown (#19651)

In this pull request we're adding an optional `tooltip` field. The
`tooltip` field is a string field (with markdown support) that will be
used to display tooltips on hover over app buttons in a workspace
dashboard.

Tooltip screenshot

<img width="816" height="275" alt="Screenshot 2025-08-29 at 4 11 56 PM"
src="https://github.com/user-attachments/assets/52c736a1-f632-465b-89a0-35ca99bd367b"
/>

Tooltip video


https://github.com/user-attachments/assets/21806337-accc-4acf-b8c6-450c031d98f1

Issue: https://github.com/coder/coder/issues/18431
Related provider PR:
https://github.com/coder/terraform-provider-coder/pull/435

### Changes

- Added migration to add `tooltip` column to `workspace_apps` table
- Updated queries to get/set the new `tooltip` column
- Updated frontend to render tooltip as markdown (primary tool tip takes
precedence over template tooltip)

### Testing

- Added storybook test for `Applink` markdown rendering

provisioner/terraform/resources.go

@@ -114,6 +114,7 @@ type agentAppAttributes struct {
 	Group       string                     `mapstructure:"group"`
 	Hidden      bool                       `mapstructure:"hidden"`
 	OpenIn      string                     `mapstructure:"open_in"`
+	Tooltip     string                     `mapstructure:"tooltip"`
 }
 
 type agentEnvAttributes struct {
@@ -589,6 +590,7 @@ func ConvertState(ctx context.Context, modules []*tfjson.StateModule, rawGraph s
 						Group:        attrs.Group,
 						Hidden:       attrs.Hidden,
 						OpenIn:       openIn,
+						Tooltip:      attrs.Tooltip,
 					})
 				}
 			}