refactor: cleanup server/runner

[evacchi]

What does this PR do?

Refactor Runner.Run() so that the logic is more straightforward: move some code to sibling funcs, refactor to a unified defer block, share the same context where possible.

Why is this change needed?

Runner.Run() is hard to understand and would benefit from a light refactoring, before we move more pieces around.

How was this tested?

All tests should still pass.

• Unit tests added/updated
• Integration/e2e tests added/updated
• Manual testing performed

Checklist

• Commits are signed off (git commit -s) per DCO
• Code follows project contributing guidelines
• Tests pass locally (make test)
• Linters pass (make lint)
• Documentation updated (if applicable)

Related Issues

follow up to #283, related to #284

[Copilot]

Pull request overview

This PR refactors Runner.Run() to make the startup/shutdown flow easier to follow by extracting cohesive helper functions and consolidating cleanup into a single deferred shutdown block.

Changes:

• Refactored Runner.Run() into a more linear sequence with helper funcs for tracer init, pool loading, flow construction, health server init, metrics server start, inference client init, and transform loading.
• Centralized shutdown/cleanup (health server, gate factory, tracer) into one deferred block that consistently runs on all exit paths.
• Improved a few error returns (notably wrapping TLS build errors and transform config/chain errors with %w).

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[shimib]

The refactor dropped the setupLog.Error(...) logs from loadWorkerPools, loadFlow, initInferenceClient (TLS), and
loadTransforms — they now just return err, and main.go handles a Run() error with a bare os.Exit(1). So a bad pool/flow/TLS/transform config now exits with no output.
Since Run has a named return, maybe log once in the existing defer:

defer func() {
if err != nil {
setupLog.Error(err, "runner failed")
}
// ...existing shutdown...
}()

Nits (non-blocking): loadTransforms should take ctx first; naked return → return nil; the new pure helpers (loadFlow, loadWorkerPools) are worth a quick unit test. The pool not found removal is fine — the merge policy already panics on an unknown pool.