fix(milo-integration): stop shipping ActivityPolicies to infra clusters

[scotwells]

Inventory's ActivityPolicies were being applied to the wrong cluster, stalling Flux on the Datum infra clusters for ~2 weeks.

The milo-integration component wires the controller into Milo, but it was also bundling 12 ActivityPolicy resources. Those need the activity.miloapis.com CRDs, which only exist on the Milo control plane — so every infra-cluster reconcile failed with no matches for kind "ActivityPolicy" and got stuck in a retry loop.

This drops the policies from milo-integration so it carries only the controller's Milo-wiring patches. The policies stay in config/milo and are applied directly to Milo by a dedicated Flux Kustomization (infra datum-cloud/infra#2737).

Verified: infra-facing build emits 0 policies and keeps all controller volumes; config/milo/activity/policies still emits all 12.

🤖 Generated with Claude Code

[ecv]

Oh well that's cool. But I was able to ship infra releases during this time, which wouldn't have been possible if Flux was stalled! A bit confused as to the effect of this mistake.

[scotwells]

@ecv may have only broke after the configs were added in? Looks like it hasn't successfully reconciled and deployed a new version since 6/4

[scotwells]

@ecv FYI getting this error now that this is being applied to Milo's API correctly:

ActivityPolicy/milo-system/inventory.miloapis.com-cluster dry-run failed (Invalid): ActivityPolicy.activity.miloapis.com "inventory.miloapis.com-cluster" is invalid: spec.eventRules[1].name: Invalid value: "not_ready": must be a valid DNS subdomain (lowercase alphanumeric and hyphens, start/end with alphanumeric): [a lowercase RFC 1123 subdomain must consist of lower case alphanumeric characters, '-' or '.', and must start and end with an alphanumeric character (e.g. 'example.com', regex used for validation is 'a-z0-9?(.a-z0-9?)*')]