Fix Nightly installer verification HTTP requests

[LunaStev]

Summary

Identify installer deployment checks with User-Agent: Wave-Nightly/1.0 and include the installer URL in network failure diagnostics. Keep the reviewed SHA-256 deployment checks unchanged.

Motivation

Wave Nightly #1 failed in the gate with HTTP Error 403: Forbidden, before any packaging job started. The installer CDN returns Cloudflare error 1010 for Python's default User-Agent; the identified Nightly client receives HTTP 200.

The companion installer change in wavefnd/wave-platform#145 is now deployed, and both live installer files match the existing reviewed hashes.

Target and compatibility impact

Nightly installer verification only. No compiler, target, ABI, archive, or installer selection changes. Network failures and hash mismatches still stop the gate before it exports package inputs.

Validation

• python3 -m unittest tools.test_nightly tools.test_ci: 38 tests passed.
• Regression coverage for the identified HTTP client, stale deployment rejection, and HTTP/connection/timeout failures for both installer URLs without gate outputs.
• Ran the gate against the original successful master CI run 37008069147: passed GitHub eligibility and both live deployment checks, exporting source 4fe815eb78d76dccffaa90000944aab86b1baadd.
• git diff --check passed.
• Did not build packages or publish a release locally. After merge, successful master CI will trigger the corrected Nightly workflow automatically.

Checklist

• Commits include a DCO Signed-off-by line.
• Tests cover new behavior or the PR explains why no test is needed.
• User-facing changes include documentation or diagnostics updates.
• The change preserves the license boundary between the compiler and std/.