The Path Forward: maintain 1.x branch for kubernetes (Identity Federation major bump)

## Background

PR [#20824](https://github.com/elastic/integrations/pull/20824) enables Identity Federation (Cloud Connectors) for the `kubernetes` package's `audit_logs` / `aws-cloudwatch` data stream. This requires raising the Kibana and Agent version floor to `^9.6.0`, which forces a major version bump from `1.x` to `2.0.0`.

Users on Kibana/Agent 9.1–9.5 cannot upgrade to `2.x`. To continue receiving bug-fixes and improvements, the `1.x` line needs a dedicated backport branch.

## What is needed

A maintainer from **@elastic/obs-ds-hosted-services** (the owning team for this package) needs to:

1. Create a branch `backport-kubernetes-1.x` from the last `1.x` release commit (tag `kubernetes-1.85.3` or the equivalent release commit).
2. Update the branch's `manifest.yml` package spec / version constraints to clearly scope it to `<9.6.0` users.
3. Publish the branch so future 1.x backport PRs can target it.

## Reference

This is the same pattern used across the AWS FI package set. See [elastic/ingest-dev#8788](https://github.com/elastic/ingest-dev/issues/8788) for the original "Path Forward" guidance.

Related PRs in this set:
- [#20822](https://github.com/elastic/integrations/pull/20822) aws_bedrock (backport issue [#20893](https://github.com/elastic/integrations/issues/20893))
- [#20817](https://github.com/elastic/integrations/pull/20817) aws_mq (backport issue [#20894](https://github.com/elastic/integrations/issues/20894))
- [#20529](https://github.com/elastic/integrations/pull/20529) aws_securityhub (backport issue [#20895](https://github.com/elastic/integrations/issues/20895))
- [#20821](https://github.com/elastic/integrations/pull/20821) aws_bedrock_agentcore (backport issue [#20922](https://github.com/elastic/integrations/issues/20922))
- [#20824](https://github.com/elastic/integrations/pull/20824) kubernetes (this issue)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Start with the kubernetes package at tag kubernetes-1.85.3 and inspect its manifest.yml version constraints. Review the AWS FI backport pattern and ingest-dev issue #8788 before creating backport-kubernetes-1.x. Done means the branch is published, scoped to users below 9.6.0, and available for future 1.x backport PRs.

Written by the indexing model from the issue text.