feat: add Reject approval policy with granular prompt rejection controls (#12087)

## Why

We need a way to auto-reject specific approval prompt categories without
switching all approvals off.

The goal is to let users independently control:
- sandbox escalation approvals,
- execpolicy `prompt` rule approvals,
- MCP elicitation prompts.

## What changed

- Added a new primary approval mode in `protocol/src/protocol.rs`:

```rust
pub enum AskForApproval {
    // ...
    Reject(RejectConfig),
    // ...
}

pub struct RejectConfig {
    pub sandbox_approval: bool,
    pub rules: bool,
    pub mcp_elicitations: bool,
}
```

- Wired `RejectConfig` semantics through approval paths in `core`:
  - `core/src/exec_policy.rs`
    - rejects rule-driven prompts when `rules = true`
    - rejects sandbox/escalation prompts when `sandbox_approval = true`
- preserves rule priority when both rule and sandbox prompt conditions
are present
  - `core/src/tools/sandboxing.rs`
- applies `sandbox_approval` to default exec approval decisions and
sandbox-failure retry gating
  - `core/src/safety.rs`
- keeps `Reject { all false }` behavior aligned with `OnRequest` for
patch safety
    - rejects out-of-root patch approvals when `sandbox_approval = true`
  - `core/src/mcp_connection_manager.rs`
    - auto-declines MCP elicitations when `mcp_elicitations = true`

- Ensured approval policy used by MCP elicitation flow stays in sync
with constrained session policy updates.

- Updated app-server v2 conversions and generated schema/TypeScript
artifacts for the new `Reject` shape.

## Verification

Added focused unit coverage for the new behavior in:
- `core/src/exec_policy.rs`
- `core/src/tools/sandboxing.rs`
- `core/src/mcp_connection_manager.rs`
- `core/src/safety.rs`
- `core/src/tools/runtimes/apply_patch.rs`

Key cases covered include rule-vs-sandbox prompt precedence, MCP
auto-decline behavior, and patch/sandbox retry behavior under
`RejectConfig`.

codex-rs/core/src/connectors.rs

@@ -104,6 +104,7 @@ pub async fn list_accessible_connectors_from_mcp_tools_with_options(
         &mcp_servers,
         config.mcp_oauth_credentials_store_mode,
         auth_status_entries,
+        &config.permissions.approval_policy,
         tx_event,
         sandbox_state,
     )