[kenfdev]

Why

Restore a maintained, testable exporter while preserving existing metrics and deployment targets. This addresses the dependency backlog in #30 and incorporates the fractional temperature-offset correction proposed by @hakonegi in #59, with regression tests.

Scope

• Support Go 1.26/1.27, update dependencies, migrate tests to Ginkgo v2 and maintained GoMock.
• Reject malformed device JSON, preserve fractional offsets, serialize per-endpoint cache refreshes, and bound HTTP requests to five seconds.
• Add remo_device_online only when the API reports a known online/offline value. Keep existing metric names, labels, configuration, and Linux amd64/arm64/ARMv7 targets.
• Replace publishing CI with build/test-only GitHub Actions. Make CircleCI inert and reject all CI calls to the manual publisher.
• Fix the Alpine override, working-directory-dependent builds, Compose/Swarm secrets, obsolete Kubernetes Deployments, and usage docs.

Tradeoffs

Electricity history and new OAuth scopes are deferred. Prometheus examples stay on 2.55.1 as an interim major-version-preserving update, not a claim of upstream support. Each HTTP request has a timeout; the complete scrape does not have a separate deadline.

Blast radius

Existing device and smart-meter metric values remain unchanged. Source builds now require Go 1.26 or later. The online metric is additive and is absent for missing/null status.

Public CircleCI job metadata confirmed branch-specific configuration and checkout revisions before publication. The first branch revision included all publication guards. CircleCI job 1478 for this exact head succeeded with only the no-publication notice, without checkout or publishing steps. The legacy tag-only publisher invocation also fails before any Docker command; the script rejects CI even with its explicit publish flag. The old CircleCI test entrypoint also fails before its subsequent Codecov upload.

Verification

• Passed race tests, vet, and Linux amd64/arm64/ARMv7 cross-builds with Go 1.26.8 and 1.27.1.
• Reproduced decoding failures, an invalid-URL panic, duplicate concurrent fetches/data races, and missing online values before their fixes; corresponding regressions now pass.
• Passed 100 repetitions of concurrent cache tests, eight packaging safety tests, module verification, and govulncheck with no findings after the update.
• Passed real-binary smoke checks for every legacy metric, fractional offsets, online false/true/null/absent, Content-Type, and cached request counts.
• Passed hosted amd64 Docker build and container smoke in GitHub Actions at head 8a217a9eaa4b0f25bac1b7b1e40dbf0c7deb8a29. Both push and PR runs passed Go 1.26/1.27 checks. Live Kubernetes and Nature hardware remain unverified. No real Nature token is used.