Option for Slack Alerts to Not send thread update to channel

### Problem Statement

Replying to the thread can be sufficient for some use cases; for those that prefer to disable this, it is considered noisy.

### Solution Brainstorm

This seems no different from disabling threads on alerts entirely, so a toggle in integration settings for alerts to still create threads but not send the reply to the channel.

Perhaps in Org Settings > Integrations > Slack > Features with the other options; see below:

### Product Area

Settings - Integrations

We want to define a set of [lightweight metrics]() that SDKs can automatically collect for e.g. framework, language or platform, focusing only on signals that **do NOT overlap with Tracing**. Ideally these metrics should give a quick sense of app or runtime health, … while deeper investigation will still rely on traces or profiles.

Examples**:**

* Node.js runtime metrics (e.g., event loop delay, heap usage)
* Prisma-related metrics in Next.js
* Mobile CPU / memory usage to help surface potential ANRs or app hangs

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**Candidate Metrics (add more below)**

* …

*(please also add ideas, questions or examples in comments)*

The issue points to Org Settings > Integrations > Slack and the alert thread reply behavior, but names no files, tests, or entry points. First trace the existing Slack alert threading and integration settings, then define the toggle's behavior; done means alerts still create threads while thread replies are not sent to the channel when disabled.

Written by the indexing model from the issue text.