README: add daily point temperatures and any-series consumers; drop internal function #142

Problem

The architecture and data sections are accurate (v0.6.7), but recent consumer capabilities are missing, and one function listed as part of the API is internal.

Findings

Shipped but not in the README (underselling)

• Daily point temperatures, cd_extract_daily() (v0.6.0), for stream-temperature and degree-day work
• Consumer functions accept any annual series, such as streamflow and stream temperature (v0.5.0)
• Per-file checksums and run provenance (v0.6.3 to v0.6.5)

Stale

• README.md:105 lists cd_stac_item() as a producer function; it is internal and not exported
• The quick start uses a toy 1951:1955 baseline (README.md:31); the vignettes use 1951:1980
• The VPD unit fix (Pa to hPa, v0.6.7) is not mentioned

Tasks

Scope widened at the plan gate (2026-10-17): rewrite the README to soul's readme.md convention in plain language, with a figure from committed code, rather than patch it. That covers the items above as follows.

• Add the shipped capabilities above, one plain clause each in the opening (no function names)
• Remove cd_stac_item() from the function list: the function table goes entirely (function tables live in the pkgdown reference)
• Use a realistic baseline (1951:1980) in the example, with its real output
• Group the _pkgdown.yml reference index by purpose. It has no reference: sections today, so the docs site shows a flat alphabetical list.
• DESCRIPTION Title/Description, README tagline and GitHub About say the same thing
• NOTICE for the ERA5-Land-derived data the package ships (CC BY 4.0)

The VPD unit fix (v0.6.7) stays in NEWS only: the convention keeps changelogs out of the README. The figure's axis-label default became #150.

Context

Audited 2026-10-14 against origin/main @ 5611c59, from README, DESCRIPTION, NEWS, NAMESPACE and vignettes. Verify each item against the code before acting. Versions cited are where a capability landed.

The New Graph website will describe this package from its README (NewGraphEnvironment/newgraphenvironment.github.io#53), so the README is the source of truth for the public one-liner. Plain language in the opening paragraph: what it does today, and what restoration planning, implementation or monitoring decision it informs.