docs: install the kit without --skill '*'

[svyatov]

What changed

• The documented install is npx skills add svyatov/oss-kit, in the README, the install guide, the site's copy button, oss-audit's Step 1, and the example README inside oss-readme. The --skill '*' flag existed to preselect nine loose rows in the picker, and 0.14.0 replaced those rows with one select-all row, so the flag now only repeats what a single keystroke does.
• skills/oss-skill/references/hosts.md said a repository documenting a whole-collection install wants --skill '*'. It now says the CLI groups a repository's skills when a plugin manifest names each skill's own directory, with the caveat that a single ./skills/ entry matches no skill directory and groups nothing.
• InstallCommand.astro drops the logic that joined --skill to its value. One span per word stays, because pre-wrap breaks after a hyphen and every hyphen left in the command sits inside a name a reader has to retype.
• Three comments in custom.css justified layout decisions by naming the flag, and now describe the constraint without it.

Why this way

The hero column stays at 0.92fr. That value was measured against the longer command, so a shorter one only adds slack, and the comment says exactly that rather than claiming a measurement nobody took.

@latest was in this change for one revision and came back out. It would have forced npx past a cached CLI old enough to miss the grouping, and it costs eight characters on the line the whole site is arranged around.

Historical CHANGELOG.md entries that record the flag being added are untouched, as is the hosts.md sentence documenting what the flag does, which is still true.

Verification

bun test 328 pass, bun run validate 0 errors, bash scripts/check-drift.sh and bun scripts/check-ecosystems.mjs clean, and the site builds 114 pages. Read back from site/dist/index.html, the hero renders npx skills add svyatov/oss-kit as four spans, so the copy handler's textContent reproduces the command exactly.

Known gaps

The grouped row itself was verified against getPluginGroupings in the CLI source during 0.14.0, not by running the installer against a published tag on this branch.

Affects

Rule or skill	Change
oss-audit	install list in Step 1, wording only
oss-readme	example README, wording only
oss-skill	hosts.md no longer recommends --skill '*' for a whole-collection install