[laodouya]

The test jobs upload coverage.txt to Codecov, and the uploads fail. In every job of the latest develop run (42150656296), and of the earlier runs checked (41794468806 on develop, 42141620869 for #10), the uploader logs Upload queued for processing failed: {"message":"Token required because branch is protected"}. codecov-action v5 defaults fail_ci_if_error to false, so the job stays green and the coverage reaches nobody. Besides, each tag set overwrites coverage.txt, so only the last one would be uploaded; file: is not an input of v5, which warns Unexpected input(s) 'file'; and the Windows job only runs go build, so it has no coverage to upload.

This removes both upload steps, the -coverprofile=coverage.txt flags that wrote the file, .codecov.yml, which only Codecov reads, and the job-level OS and GO variables. Their only reader was the upload's env_vars: OS,GO: no step reads them, and the example Makefiles that read OS do not run in CI. The tests themselves run as before, with every tag set and -race.

Left out:

• The Codecov badge in the README: it is in the README of go-sqlite3, quoted below this fork's section, and shows go-sqlite3's own coverage.
• Fixing the upload with a token instead: nothing reads the coverage, and the user chose to delete it.
• The Windows job still only builds, and no Unix job uses sqlite_omit_localtime; both predate this change.

Testing

• GitHub Actions on this branch: all six jobs pass, and their steps end with Tags: vacuum, with no upload step (run 42162795021).
• On linux/amd64 (Debian trixie container cql-ci:go1.27 plus libsqlite3-dev), Go 1.27.3, --cpus 4: the four go test commands, taken from the workflow file as written (go test -race -v -tags "", -tags "libsqlite3", the full set, -tags "sqlite_vacuum_full"), pass, and none writes a coverage.txt.