fix: preserve GPT Image 2 auto failover defaults

[lingozhi]

Summary

• preserve the documented GPT Image 2 size=auto tuple as a contract wildcard
• keep its resolved defaults compatible with the unchanged KIE backup profile
• retain the strict 36-tuple fixed-size matrix and the existing 1K/auto/auto compatibility path
• keep the exception limited to gpt-image-2 generation-only production-verified profiles

Production bug

The full matrix profile encoded auto as 1K/auto/auto, while channel 127 intentionally retains generation,size=auto. Candidate default consistency runs before priority selection, so a caller that sends only size=auto receives must specify resolution instead of selecting Opwan and preserving KIE failover.

Verification

• RED: DTO validation rejected the contract wildcard and channel selection chose 127 instead of primary 117
• GREEN: focused DTO + channel selection regression tests pass
• go test ./dto ./model -count=1
• go test ./... -count=1

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Prevent the auto tuple from wildcarding explicit geometry

When this newly permitted tuple is combined with the fixed GPT Image 2 matrix, an explicit unsupported request such as resolution=4K, aspect_ratio=3:2 matches {generation, size:auto} because ImageRoutingCombination.matches treats its empty resolution and aspect ratio as wildcards. ApplyDefaults then resolves the request to size=auto, so Supports accepts it despite the matrix lacking that tuple; the images_generations path strips the geometry aliases and sends only size=auto, while billing retains the requested 4K resolution. Thus users can be charged for 4K while receiving the provider's automatic geometry. The exception must apply only when geometry was not explicitly requested, rather than admitting a generally matching combination.

AGENTS.md reference: AGENTS.md:L119-L119

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