Follow-up to #26862 ("remove direct chat routing"), which collapsed the
routing discriminated union into a single `aiGatewayModelRoute` but left
a one-path dispatch shim behind in `model_routing.go`.
Removes
`resolveModelRouteForConfig`/`resolveModelRouteForProviderType`/`newModel`
wrapper functions that did nothing but call their `*AIGateway*`
counterparts, and renames the `*AIGateway*` targets to take over those
names directly. Also collapses a redundant if/else in
`title_override.go` where both branches called the same function with
the same effective argument, and has `chatutil.NormalizedStringPointer`
delegate to the existing `coderd/util/strings.EmptyToNil` instead of
reimplementing empty-string-to-nil logic.
No behavior change.
<details>
<summary>Investigation notes / decision log</summary>
Two independent read-only investigations were run over `coderd/x/chatd`
looking for cleanup opportunities following #26862: one focused on
residue from that PR specifically, one a general over-engineering pass
on the whole package. Both independently converged on the
`model_routing.go` shim as the top finding (verified zero divergent call
sites).
Other candidates considered and explicitly deferred/rejected for this
PR:
- Renaming away the vestigial `AIGateway` prefix package-wide:
cosmetic-only, touches many call sites, skipped.
- Inlining the `chatcost` subpackage into `chatd`: unrelated to #26862,
skipped.
- Deleting the deprecated `AIGatewayRoutingEnabled` deployment flag:
confirmed dead/no-op, but intentionally kept as a back-compat shim per
#26862; removal should follow the same deprecation cadence as other
deprecated deployment options, as a separate, differently-timed change.
- Folding `chatutil` entirely into `chatprovider`/`chatopenai`:
`NormalizedStringPointer` overlapped with
`coderd/util/strings.EmptyToNil` (now reused), but `NormalizedEnumValue`
has no equivalent elsewhere in the repo and still has 2 real call sites,
so the package stays.
</details>
---
Generated by Coder Agents on behalf of @johnstcn.
Cian Johnston
843754a547