Suppress the first-level numbering

[Akira]

I have

#set heading(numbering: "1.A.1.")
#set text(lang: "fr")
#set text(size: 12pt)

= Chapter 1

== Section title

=== Section title

= Chapter 2

== Section title

=== Section title

that produces the numbering

1. Chapter 1
1.A. Section title
1.A.1. Section title
2. Chapter 2
2.A. Section title
2.A.1. Section title

I would like to ask how to suppress the first-level numbering, i.e., to obtain

Chapter 1
A. Section title
A.1. Section title
Chapter 2
A. Section title
A.1. Section title

and make the first-level heading centered. Here they are Chapter 1 and Chapter 2.

Thank you for your elaboration.

[hpcfzl]

This really appears to be different from How can I prevent level 1 headings from being numbered?. By using the set rule from there, this is what I think could be viable:

#show heading.where(level: 1): it => block(it.body)
#set heading(numbering: (first, ..nums) => numbering("A.1.", ..nums))

= Chapter 1

== Section title

=== Section title

= Chapter 2

== Section title

=== Section title

Output

So the first-level heading still has numbering, it’s simply not visible due to its show rule.

---

@Akira

… the first-level heading centered.

Apply this change:

- #show heading.where(level: 1): it => block(it.body)
+ #show heading.where(level: 1): it => align(center, block(it.body))

Or add this:

#show heading.where(level: 1): set align(center)

[Akira]

@hpcfzl

align(center, block(it.body))

Thank you very much for your solution.