docs: correct two contributor instructions that the source contradicts

Both P1s from Miguel's review on #2976.

**The weekly changelog command has a fourth output, and it is public.**
`changelog-process.mdx` listed three internal drafts. `outputWeeklyDraft` also
calls `prependDocsUpdate` on `--write` (`scripts/changelog-weekly.ts:236`),
which writes straight into `docs/weekly-updates.mdx`. A contributor following
the page would review three files and push a fourth unread. Now called out as a
warning, with the re-run behaviour, since that is what makes editing the entry
afterwards safe.

The same paragraph also said Weekly updates is "unlisted in the sidebar". That
was true when written and I made it false myself, putting the page back under
Explore in #2978 after Rames found it orphaned. Corrected rather than reverted —
the page belongs in the sidebar.

**Bare `hyperframes lint` cannot validate a registry item.** Both
`contributing.mdx` and `contributing/catalog.mdx` told contributors to run it.
The CLI resolves a project by looking for `index.html`
(`packages/cli/src/utils/project.ts`), and registry items ship as `<name>.html`
or `demo.html`, so it fails with "No composition found". This is not
theoretical: `scripts/lint-registry-items.mjs` exists precisely for this shape
and its header records two `gsap_non_transform_motion` errors that reached main
unlinted because of it.

Both pages now document `bun run lint:registry-items`, and the Catalog page
shows the install-into-a-scratch-project route for the full `check` gate rather
than claiming a bare `check` covers a registry item.

Verified by running the documented command, not just by reading the script.

Author: ukimsanov

docs/contributing.mdx

@@ -33,11 +33,23 @@ bun run --filter '*' typecheck
 bun run test
 ```
 
-For a composition or registry item, also run:
+For a composition, run the gates from the project directory, or pass it:
 
 ```bash
-npx hyperframes lint
-npx hyperframes check
+npx hyperframes lint ./my-video
+npx hyperframes check ./my-video
+```
+
+Registry items need a different command. They ship as `<name>.html` or
+`demo.html`, and the CLI resolves a project by looking for `index.html`, so
+pointing it at an item directory fails with "No composition found" — which is
+how two `gsap_non_transform_motion` errors once reached `main` unlinted. Use the
+script that mounts each item into a throwaway project first, exactly where
+`hyperframes add` would put it:
+
+```bash
+bun run lint:registry-items              # every item
+bun run lint:registry-items my-block     # just one
 ```
 
 The pre-commit hooks format staged files and run checks for the files you changed.

docs/contributing/catalog.mdx

@@ -101,10 +101,19 @@ A one-off example belongs in [Examples](/examples), not the Catalog.
 
 ## Validate and preview
 
-Run the composition gates:
+Lint the item the way a user receives it — mounted into a real project. A bare
+`npx hyperframes lint` cannot validate a registry directory, because the CLI
+looks for `index.html` and items ship as `<name>.html` or `demo.html`:
 
 ```bash
-npx hyperframes lint
+bun run lint:registry-items my-block
+```
+
+To exercise the full gate, install the item into a scratch project and run there:
+
+```bash
+npx hyperframes init scratch && cd scratch
+npx hyperframes add my-block
 npx hyperframes check
 ```
 

docs/contributing/changelog-process.mdx

@@ -93,13 +93,21 @@ bun run changelog:weekly --from 2026-06-01 --to 2026-06-07 --write
 
 Run it from an up-to-date `main` branch so the selected range reflects public history, not a feature branch.
 
-This creates internal editorial drafts:
+This writes three internal editorial drafts:
 
 - `updates/weekly/2026-06-07.md`
 - `updates/social/2026-06-07.discord.md`
 - `updates/social/2026-06-07.x.md`
 
-Review and rewrite the generated files before publishing anything. Social drafts are never posted automatically. Curated highlights from these packets go to [Weekly updates](/weekly-updates), which is unlisted in the sidebar and reachable by URL and RSS; exact versioned release notes stay in the [Changelog](/changelog).
+<Warning>
+  It also writes a fourth file, and that one is public. `--write` prepends the
+  generated entry straight into `docs/weekly-updates.mdx`, which ships in the
+  sidebar under **Explore**. Review that diff with the same care as the page it
+  is — it is not a draft. Re-running for a range already present is a no-op, so
+  the entry is safe to edit in place afterwards.
+</Warning>
+
+Review and rewrite all four before publishing anything. Social drafts are never posted automatically. Exact versioned release notes stay in the [Changelog](/changelog); [Weekly updates](/weekly-updates) carries the curated highlights and an RSS feed.
 
 ## Writing style