feature request: Some form of cli-agent config global default or inheritance pattern

This is a feature request for some form of global cli-agent config or inheritance mechanism.

There are a lot of configurations for cli-agents that are going to be global standards for a user's use case without the ability to define some form of default or inheritance pattern we will find users will need to create lots of agent files that have 90% of the lines being identical with only a few lines being unique.

Ex. A user may have a list of MCP servers they globally use but when they what the agent to be front end centric they will also include a front end MCP service like stencil MCP. Inversely they might have AWS SDK MCP servers when working on Backend tasks. This problem gets worse when you have standard hooks like
```
"userPromptSubmit": [
{
"command": "date -u +\"%Y-%m-%dT%H:%MZ\"",
"timeout_ms": 30000,
"max_output_size": 10240,
"cache_ttl_seconds": 0
}
]
```
where the user want's the AI Agent to have an accurate timestamp.

This becomes especially problematic when adding new changes to each agent config.

Without this feature users will be pressured into avoiding using cli-agents and instead working on some global users which will be less effective as it tries to do to many things polluting its context window with irrelevant tools and context files.

Non vengono indicati file, test o punti di ingresso. Inizia individuando i percorsi di caricamento ed ereditarietà della configurazione di cli-agent, quindi esamina la documentazione di configurazione esistente; done dovrebbe includere un modello di ereditarietà concordato, regole di precedenza e la copertura dei valori predefiniti globali e degli override specifici dell'agente.

Scritto dal modello di indicizzazione a partire dal testo della issue.