docs(cli): clarify password field limitations for main branch (supabase#5309)

Updates the help text for the `branches get` command in both the Go and
TypeScript CLI implementations to clarify that password-dependent
database fields are not populated for the main branch.

**Changes:**
- Updated `branchGetCmd` long description in
`apps/cli-go/cmd/branches.go` to include a note explaining that
`POSTGRES_URL` and `POSTGRES_URL_NON_POOLING` fields are not available
for the main branch because production database credentials cannot be
retrieved via API
- Updated the command description in
`apps/cli/src/legacy/commands/branches/get/get.command.ts` with the same
clarification for consistency across CLI implementations

This improves user experience by setting correct expectations when
querying main branch details and reduces confusion about missing
credential fields.

Closes: CLI-1450

https://claude.ai/code/session_01Dq9V9d8nxzfFkqk3MaHBWB

---------

Co-authored-by: Claude <noreply@anthropic.com>

Author: avallete

apps/cli-go/cmd/branches.go

@@ -78,8 +78,10 @@ var (
 	branchGetCmd = &cobra.Command{
 		Use:   "get [name]",
 		Short: "Retrieve details of a preview branch",
-		Long:  "Retrieve details of the specified preview branch.",
-		Args:  cobra.MaximumNArgs(1),
+		Long: `Retrieve details of the specified preview branch.
+
+Note: For the main branch, password-dependent fields (POSTGRES_URL, POSTGRES_URL_NON_POOLING) are not populated because production database credentials are not retrievable via API.`,
+		Args: cobra.MaximumNArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {
 			ctx := cmd.Context()
 			fsys := afero.NewOsFs()

apps/cli/src/legacy/commands/branches/get/get.command.ts

@@ -16,7 +16,9 @@ const config = {
 export type LegacyBranchesGetFlags = CliCommand.Command.Config.Infer<typeof config>;
 
 export const legacyBranchesGetCommand = Command.make("get", config).pipe(
-  Command.withDescription("Retrieve details of the specified preview branch."),
+  Command.withDescription(
+    "Retrieve details of the specified preview branch.\n\nNote: For the main branch, password-dependent fields (POSTGRES_URL, POSTGRES_URL_NON_POOLING) are not populated because production database credentials are not retrievable via API.",
+  ),
   Command.withShortDescription("Retrieve details of a preview branch"),
   Command.withHandler((flags) => legacyBranchesGet(flags)),
 );