feat(worker): support per-replica replicaCount override

[michaellzc]

Summary

Follow-up to #582, which added support for scaling worker horizontally by configuring dedicated replicas per set of jobs.

This PR adds a replicaCount override for each distinct worker replica. Previously every generated worker deployment (the primary worker and each dedicated worker-N) inherited the single top-level worker.replicaCount. Now each entry under worker.replicas can set its own replicaCount, falling back to worker.replicaCount when unset.

This lets operators scale individual dedicated workers horizontally only for jobs that are safe to scale that way.

worker:
  replicas:
    - replicaCount: 3 # make sure jobs are safe to scale horizontally
      jobs:
        - job1
        - job2
    - jobs:
        - job3 # inherits worker.replicaCount

Changes

• templates/_worker.tpl: added a $replicaCount parameter to the sourcegraph.worker helper and use it for spec.replicas.
• templates/worker/worker.Deployment.yaml: pass worker.replicaCount for the primary worker, and per-replica replicaCount (defaulting to worker.replicaCount) for each dedicated replica.
• values.yaml: documented the new per-replica replicaCount option.
• tests/worker_test.yaml: added tests covering the default-inheritance and per-replica override behaviour.
• CHANGELOG.md: added an entry.

Test plan

• helm unittest charts/sourcegraph — all 99 tests pass (7 in the worker suite).
• ./scripts/helm-docs.sh produces no uncommitted changes.

Slack thread: https://sourcegraph.slack.com/archives/C0ATB8N5P3Q/p1781106413632049

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Generated by Claude Code

[filiphaftek]

Nice!