Fix OIDC credential property names

[mbg]

Fixes an oversight in #3563. The JSON property names use - instead of _.

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Merge / deployment checklist

• Confirm this change is backwards compatible with existing workflows.
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[Copilot]

Pull request overview

This PR corrects the JSON property names used for OIDC credential configurations in the start-proxy action, switching from underscore-separated keys to hyphen-separated keys to match the expected schema.

Changes:

• Update OIDC config types and validators (Azure/AWS/JFrog) to use hyphenated JSON keys.
• Update getAuthConfig and credential pretty-printing to read/write the new keys.
• Update unit tests to use the new key names (and regenerate lib/ output).

Show a summary per file

File	Description
src/start-proxy/types.ts	Switches OIDC config typing/validation and pretty-printing to hyphenated JSON property names.
src/start-proxy/types.test.ts	Updates fixtures/expectations for OIDC credential string formatting with new keys.
src/start-proxy.ts	Updates getAuthConfig normalization/output for OIDC configs to use hyphenated keys.
src/start-proxy.test.ts	Updates OIDC test fixtures to use the new hyphenated keys.
lib/start-proxy-action.js	Generated build output reflecting the TypeScript changes.

Copilot's findings

• Files reviewed: 4/5 changed files
• Comments generated: 3

[henrymercer]

Changelog note?