apps: Surface init, manifest, validate, and dev-remote in --help (databricks#5276)

## Summary
- Remove `Hidden: true` from four AppKit-related custom commands on
`databricks apps` so they appear under "Available Commands" in `--help`:
  - `init` — initialize a new AppKit application from a template
  - `manifest` — print the template plugin manifest
  - `validate` — validate a Databricks App project
- `dev-remote` — run AppKit app locally with WebSocket bridge to remote
- All four are already implemented, documented, and invokable today —
hiding them just makes them undiscoverable through `apps --help`.

## Test plan
- [x] `go build` succeeds
- [x] `./cli apps --help` lists `init`, `manifest`, `validate`, and
`dev-remote` under "Available Commands"
- [x] `./cli apps <cmd> --help` still works for each (unchanged)

Note: I left the `*-space` / `*-app-thumbnail` workspace API commands
hidden — those are auto-generated and explicitly gated as
PRIVATE_PREVIEW, separate concern.

This pull request and its description were written by Isaac.

Author: atilafassina

cmd/apps/dev.go

@@ -120,9 +120,8 @@ func newDevRemoteCmd() *cobra.Command {
 	)
 
 	cmd := &cobra.Command{
-		Use:    "dev-remote",
-		Short:  "Run AppKit app locally with WebSocket bridge to remote server",
-		Hidden: true,
+		Use:   "dev-remote",
+		Short: "Run AppKit app locally with WebSocket bridge to remote server",
 		Long: `Run AppKit app locally with WebSocket bridge to remote server.
 
 Starts a local Vite development server and establishes a WebSocket bridge

cmd/apps/init.go

@@ -81,9 +81,8 @@ func newInitCmd() *cobra.Command {
 	)
 
 	cmd := &cobra.Command{
-		Use:    "init",
-		Short:  "Initialize a new AppKit application from a template",
-		Hidden: true,
+		Use:   "init",
+		Short: "Initialize a new AppKit application from a template",
 		Long: `Initialize a new AppKit application from a template.
 
 When run without arguments, uses the default AppKit template and an interactive prompt

cmd/apps/manifest.go

@@ -96,9 +96,8 @@ func newManifestCmd() *cobra.Command {
 	)
 
 	cmd := &cobra.Command{
-		Use:    "manifest",
-		Short:  "Print template manifest with available plugins and required resources",
-		Hidden: true,
+		Use:   "manifest",
+		Short: "Print template manifest with available plugins and required resources",
 		Long: `Resolves a template (default AppKit repo or --template URL), locates appkit.plugins.json,
 and prints its raw contents to stdout. No workspace authentication is required.
 

cmd/apps/validate.go

@@ -12,9 +12,8 @@ import (
 
 func newValidateCmd() *cobra.Command {
 	cmd := &cobra.Command{
-		Use:    "validate",
-		Short:  "Validate a Databricks App project",
-		Hidden: true,
+		Use:   "validate",
+		Short: "Validate a Databricks App project",
 		Long: `Validate a Databricks App project by running build, typecheck, and lint checks.
 
 This command detects the project type and runs the appropriate validation: