chore(release): add OIDC availability diagnostic

[cipolleschi]

Temporary diagnostic to disambiguate the ENEEDAUTH publish failure.

Adds a step that prints whether ACTIONS_ID_TOKEN_REQUEST_URL is present (presence only — never the value). GitHub only injects that env var when id-token: write is actually granted.

After merging, re-run the Release workflow and read the Debug OIDC availability step:

• "OIDC id-token IS available" → id-token is granted; the remaining issue is the npm trusted-publisher config on npmjs.com.
• "OIDC id-token is NOT available" → GitHub still isn't granting id-token; the restriction is at the enterprise level (org workflow permissions are already read/write).

Revert this once the release is green.