Triage the first measured idle controller writes

**What is this about?**

#44250 provides the controller, write size, frequency, and idle flag. This task traces each leading entry to the state change that caused it. Prefer removing an unnecessary write or persisted field when the code allows it.

## Goal

Trace each leading idle write to its state change and assign any follow-up to the owning team.

## Before implementation

Before writing code, try to prove this issue is not worth doing. Make the requirement less dumb before optimizing anything. Look for code, state, or writes we can delete. If deletion does not solve it, prefer a smaller change using what already exists. Record the finding and close the issue if the proposal no longer makes sense.

## Open questions

- What controller update causes each leading idle write?
- Is the update required background behavior?
- Which team owns the state and the update?

**Technical Details**

The E0 measurements and dashboard in #44250 provide the first results.

**Acceptance Criteria**

- [ ] The leading idle-write sources have an owner and an explanation.
- [ ] Each approved change has its own issue and names the write it will remove or reduce.
- [ ] Required background writes are documented as exceptions.

**Stakeholder review needed before the work gets merged**

- [ ] Engineering (needed in most cases)
- [ ] Design
- [ ] Product
- [ ] QA (automation tests are required to pass before merging PRs but not all changes are covered by automation tests - please review if QA is needed beyond automation tests)
- [ ] Security
- [ ] Legal
- [ ] Marketing
- [ ] Management (please specify)
- [ ] Other (please specify)

**References**

- Parent: #44253
- E0 measurements and dashboard: #44250

Start with the E0 measurements and dashboard in #44250, then use the controller, write size, frequency, and idle flag to trace each leading idle write to its triggering state change. Record whether each write is required, identify the owning team, and document exceptions. Any approved code change should become a separate issue naming the write it will remove or reduce, with review coordinated through the stated stakeholder requirements.

Written by the indexing model from the issue text.