[dajiaohuang]

Correct two existing CTD help statements to match the public API:

• as.ctd() subtracts pressureAtmospheric from pressure; its pressure argument description currently says it stores their sum, contradicting both the implementation and the pressureAtmospheric argument description.
• The sigmaTheta accessor computes swSigmaTheta(x), not swTheta(x), and it takes precedence over a stored sigmaTheta item (rather than a stored theta item).

Only canonical roxygen comments and their generated Rd files change. Regenerated with the package's recorded roxygen2 7.3.2; no other generated changes.

Validation: R 4.3.3 / Ubuntu 24.04, synthetic public-API calls verified pressure subtraction and that computed sigmaTheta overrides a deliberately stored value. Both changed Rd files pass tools::checkRd. Runtime code is unchanged; the same base's build/install/load and representative synthetic usage were checked during this pass. Full upstream tests/examples, vignettes and manual generation were not run.

[richardsc]

Thanks for catching these. They look good to me -- I'll wait for @dankelley to approve before merging.

[dankelley]

@Clark, I clicked 'approve'. But please wait for those CI checks to complete before merging. They can be slow -- maybe just check this afternoon.

[dankelley]

Oh, I meant @richardsc ... sorry to whoever "at"clark might be!

[richardsc]

Checks passed, I'll merge. Thanks!