docs(airflow_tags): add impact/tier_0 and update tier SLA descriptions

docs/reference/airflow_tags.md

@@ -11,10 +11,11 @@ More information and the discussions can be found the the original Airflow Tags
 
 ### impact/tier tag
 
-We borrow the [tiering system](https://wiki.mozilla.org/Sheriffing/Job_Visibility_Policy#Overview_of_the_Job_Visibility_Tiers) used by our integration and testing sheriffs. This is to maintain a level of consistency across different systems to ensure common language and understanding across teams. Valid tier tags include:
+We adapt the [tiering system](https://wiki.mozilla.org/Sheriffing/Job_Visibility_Policy#Overview_of_the_Job_Visibility_Tiers) used by our integration and testing sheriffs. This is to maintain a level of consistency across different systems to ensure common language and understanding across teams. Valid tier tags include:
 
-- **impact/tier_1**: Highest priority/impact/critical DAG. A job with this tag implies that many downstream processes are impacted and affects Mozilla’s (many users across different teams and departments) ability to make decisions. A bug ticket must be created and the issue needs to be resolved as soon as possible.
-- **impact/tier_2**:  Job of increased importance and impact, however, not critical and only limited impact on other processes. One team or group of people is affected and the pipeline does not generate any business critical metrics. A bug ticket must be created and should be addressed within a few working days.
+- **impact/tier_0**: Foundational pipelines that a significant portion of downstream data processing depends on (e.g. copy dedupe, Glean usage). A Tier 0 failure takes priority over all other work — all hands on deck, must fix ASAP. A bug ticket must be created immediately and the issue worked until it is resolved or explicitly handed off to someone who has accepted ownership.
+- **impact/tier_1**: Business-critical pipelines: those supporting key daily reporting, important product functionality, or time-sensitive processes such as data sent to external systems or marketing ad platforms. A bug ticket must be created and the issue is expected to be resolved within hours, no later than the end of the same business day.
+- **impact/tier_2**: Important pipelines supporting established, actively used workflows that are not time-sensitive, such as external data feeds (app store reviews, Reddit, etc.), where a short delay is acceptable but an extended outage would affect planned work. A bug ticket must be created and the issue is expected to be resolved within 2–3 business days.
 - **impact/tier_3**: No impact on other processes and is not used to generate any metrics used by business users or to make any decisions. A bug ticket should be created and it’s up to the job owner to fix this issue in whatever time frame they deem to be reasonable.
 
 ### triage/ tag