[Chapter: Vertices and Edges] Improve vertex ID logic to reuse highest-numbered ID

[moody-jazz]

Currently, when a vertex is removed, the next added vertex always receives a new incremented ID, even if the highest-numbered vertex was deleted.

For example:

• Add v1 to v5 → delete v5 → add a new vertex → it becomes v6 (instead of reusing v5).

Suggestion: Update the logic so that if the highest-numbered vertex is removed, its ID is reused.