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Please help me complete the update (Update/Modify) service business code for the `System Platform` object.

An entity update is not a partial DTO patch. Load every scalar field before
modification so the checker can validate the complete business state. Do not
load the mutation target with a minimal request or a reduced `select_xxx()`
projection: if you have not seen the complete entity, you must not change it.

To ensure absolute correctness of the API, please refer to and strictly imitate the following **real update code example for `System Platform`**.

### Standard Update Example (Reference)
Please carefully observe the querying mechanism, the `update_xxx()` property setting methods, and the strictly required `.audit_as()` and `.save()` cascade in the example code:

```rust
use crm_erp_service_core::teaql_core::Entity;
use crm_erp_service_core::{Q, Platform, TeaqlRuntime, AuditedSave};

pub async fn update_example(
    context: &impl TeaqlRuntime,
    entity_id: u64,
    new_name: String,
    new_create_time: teaql_core::time::Timestamp,
    new_last_update_time: teaql_core::time::Timestamp,

) -> Result<Option<Platform>, Box<dyn std::error::Error>>
{
    let Some(mut existing_entity) = Q::platforms()
        .with_id_is(entity_id)

        .comment("what: Find entity for modification")
        .purpose("why: Need to update properties")
        .execute_for_one(context)
        .await?
    else { return Ok(None); };

    existing_entity.update_name(new_name);
    existing_entity.update_create_time(new_create_time);
    existing_entity.update_last_update_time(new_last_update_time);


    let persisted = existing_entity
        .audit_as("business reason: update authorized fields")
        .save(context).await?;

    Ok(Some(persisted))
}
```

### Your Task
Please completely imitate the framework, imports, and syntax features of the above code to implement the real update logic for `System Platform` based on my specific business needs. Please output the Rust source code directly.

**CRITICAL**: We have already generated the correct plural/singular form for the `Q::` method in the example above. Copy its EXACT spelling. Do not replace it with the `_minimal()` form or add a reduced projection for an entity that will be saved.


---

## TeaQL seven-language assist contract

Apply the verified Rust semantic ceiling while using only the exact RUST generated and
runtime APIs. Discover APIs through the generated application AGENTS.md and progressive
model-aware Assist. Do not inspect generated domain-library source.

- Do not create plurals by appending `s` or `es`; use the centralized generated plural.
- Human and non-human entities use different generated predicate vocabularies. Preserve
  forms such as “who are active” and “whose email is”; never infer them from English.
- Configure filters, projection, paging, and other query options before `purpose(...)`.
  Comment may appear anywhere in the chain. Purpose enters the executable stage; execution
  requires both values, but comment does not have to immediately precede purpose.
- Every execute/list/stream and every save accepts exactly one context argument:
  `UserContext`. Name that argument `context`, never `runtime`; data services and global
  policy are injected when the context is built. Reserve `runtime` for process-level
  runtime ownership, provider/pool setup, and module assembly.
- Tenant, merchant, identity, permissions, request policy, purpose policy, hard limit,
  and continuous-page cursor policy come only from trusted context, never dynamic JSON or TFP.
- If the required operation is absent after current entity/action and required field
  Assist, stop that path and report MISSING_ASSIST. Do not guess an API or search the
  generated library as a fallback.
- Create each application-owned source file once. After its first compile attempt,
  repair only the smallest block identified by the exact compiler or test diagnostic.
  Preserve unrelated code; do not rewrite the complete file as an error-recovery loop.
- Before a repair that would replace more than 25% of an existing application file,
  stop and report LARGE_REWRITE_REQUEST with the file, exact diagnostic, reason, and
  estimated scope. Initial creation and model-driven regeneration are not repairs.

Capability: `update`.

- Load the tenant-scoped current entity first so its original version participates
  in optimistic locking; do not reconstruct versioned state from untrusted JSON.
- Allow-list writable fields, attach the generated audit-reason API, and save with
  the same UserContext. Add a stale-version rejection test.