fix(bazel): surface swallowed Close and logger-init errors

[sbalabanov]

Summary

Fixes several swallowed-error issues found while auditing the codebase for dropped errors.

core/bazel/bazel.go — bazelisk download install path

The temp-file-then-rename dance exists specifically to avoid installing partial binaries, but three ignored errors undermined it:

1. Success-path tmp.Close() was ignored. A failed flush (disk full, network filesystem) could leave a truncated file that was then chmod'd and rename'd into place. Its error is now checked and propagated.
2. io.Copy error path discarded tmp.Close(). It is now folded into the returned error via errors.Join.
3. defer os.Remove(tmpPath) ignored its error and ran on every path — including success, where the file had already been renamed away, guaranteeing an ENOENT. Cleanup now runs only on failure (via a named-return defer) and joins any removal error into the result.

example/main.go and example/client/client.go

Discarded zap.NewDevelopment() error: zl, _ := zap.NewDevelopment() followed by defer zl.Sync() would nil-panic on the (rare) init failure. The server returns the wrapped error from run(); the client prints to stderr and exits, matching its existing main() style.

Testing

• make build — passes
• make test — all 14 test targets pass
• make gazelle — no BUILD changes

🤖 Generated with Claude Code

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