feat: add app status tracking to the backend (#17163)

This does ~95% of the backend work required to integrate the AI work.

Most left to integrate from the tasks branch is just frontend, which
will be a lot smaller I believe.

The real difference between this branch and that one is the abstraction
-- this now attaches statuses to apps, and returns the latest status
reported as part of a workspace.

This change enables us to have a similar UX to in the tasks branch, but
for agents other than Claude Code as well. Any app can report status
now.

codersdk/agentsdk/agentsdk.go

@@ -581,6 +581,28 @@ func (c *Client) PatchLogs(ctx context.Context, req PatchLogs) error {
 	return nil
 }
 
+// PatchAppStatus updates the status of a workspace app.
+type PatchAppStatus struct {
+	AppSlug            string                           `json:"app_slug"`
+	NeedsUserAttention bool                             `json:"needs_user_attention"`
+	State              codersdk.WorkspaceAppStatusState `json:"state"`
+	Message            string                           `json:"message"`
+	URI                string                           `json:"uri"`
+	Icon               string                           `json:"icon"`
+}
+
+func (c *Client) PatchAppStatus(ctx context.Context, req PatchAppStatus) error {
+	res, err := c.SDK.Request(ctx, http.MethodPatch, "/api/v2/workspaceagents/me/app-status", req)
+	if err != nil {
+		return err
+	}
+	defer res.Body.Close()
+	if res.StatusCode != http.StatusOK {
+		return codersdk.ReadBodyAsError(res)
+	}
+	return nil
+}
+
 type PostLogSourceRequest struct {
 	// ID is a unique identifier for the log source.
 	// It is scoped to a workspace agent, and can be statically