fix(github): normalize hostnames before credential lookup and API routing - #1069

Summary

A mixed-case GitHub.com hostname could select Enterprise Server REST and GraphQL paths. Normalize the hostname before credential lookup and endpoint selection so casing does not change the selected GitHub platform.

Changes

• Merge the latest main into the contributor branch, preserving its history and existing Enterprise Cloud routing.
• Normalize the hostname once and simplify the API base URL selection.
• Consolidate duplicate endpoint tests into a REST/GraphQL matrix covering GitHub.com, Enterprise Cloud with data residency, and Enterprise Server, including explicit ports.
• Add a synthetic gh child-process regression test for the hostname used in credential lookup.

Testing

• Reproduced incorrect mixed-case GitHub.com REST/GraphQL paths on main; verified the corrected paths. The credential regression also fails when hostname normalization is removed.
• Focused GitHub/import/discovery tests: 58 passed, 3 platform skips in both fixed and randomized order.
• Full SDK suite: 4,904 passed, 65 skipped, zero failures in both fixed and randomized order on the final head.
• Full SDK types, formatting, plugin build, and build:ci passed.
• Three fresh independent source reviews and separate verification found no actionable issues on the final commit.

Risk and rollout

Compatible bug fix with no new commands, flags, or settings. Existing platform endpoints, token protections, and cancellation behavior are preserved. Endpoint tests use the real Octokit client with synthetic credentials and injected transport; live Enterprise instances were not exercised.

Public disclosure review

• No customer, partner, prospect, or user identities, data, or identifying details are included.
• No credentials, personal data, private source, scan findings, or nonpublic links or tickets are included.
• I reviewed the branch name, title, description, commits, changes, comments, logs, screenshots, attachments, and links for public disclosure.