docs (Skills): stop assuming app/ at the root and port 3000 - #96696

…6696)

### What?

Two Skills assumed a default project layout, and both failed silently
when it didn't hold.

- `next-cache-components-adoption` hardcoded `./app` for the
`cache-components-instant-false` codemod, and checked its work under
`app/` too. It now resolves the app directory from `next.config.*` and
reads the file count the codemod reports.
- `next-dev-loop` probed `/_next/mcp` in preflight, but `NEXT_MCP_URL`
for a non-default port was only mentioned much later. The port is now
resolved before the first probe.

The same `./app` argument is documented for both 16.3 codemods, so the
two guides and the codemods reference get a matching Good to know.

### Why?

On a `src/app` project the codemod matched nothing and no gate caught
it. A path that doesn't exist isn't an error for jscodeshift: it prints
`No files selected, nothing to do`, reports `0 ok`, and exits `0`. The
root-layout check looked in the same wrong place, and if the app's
routes were prerenderable the build passed too, so a repo the migration
never touched came out green.

On a dev server bound to another port, the preflight probe read
"unreachable" and refused to verify while `next dev` was running.

Both are silent failures, which is the worst case for instructions an
agent runs top to bottom.

### How?

- Anchor on `next.config.*` so an agent invoked from a subdirectory
doesn't test for `app/` against the wrong `cwd`.
- When `app/` and `src/app/` both exist, say so: Next.js builds `app/`
and never reads `src/app/`, so those routes are shadowed and unbuilt.
Ask which tree to migrate.
- Treat `0 ok` as a wrong path rather than a finished run.
- Move the `NEXT_MCP_URL` resolution into the `next-dev-loop` preflight.

The transforms are fine. Their path regexes match `src/app/...`, and
pointed at `./src/app` they convert every segment.
`remove-partial-prefetch` has the same shape and hardcoded path, so it's
covered here too.

Fixes vercel#96649

---------

Co-authored-by: Claude Opus 5 <noreply@anthropic.com>

### What?

Two Skills assumed a default project layout, and both failed silently
when it didn't hold.

- `next-cache-components-adoption` hardcoded `./app` for the
`cache-components-instant-false` codemod, and checked its work under
`app/` too. It now resolves the app directory from `next.config.*` and
reads the file count the codemod reports.
- `next-dev-loop` probed `/_next/mcp` in preflight, but `NEXT_MCP_URL`
for a non-default port was only mentioned much later. The port is now
resolved before the first probe.

The same `./app` argument is documented for both 16.3 codemods, so the
two guides and the codemods reference get a matching Good to know.

### Why?

On a `src/app` project the codemod matched nothing and no gate caught
it. A path that doesn't exist isn't an error for jscodeshift: it prints
`No files selected, nothing to do`, reports `0 ok`, and exits `0`. The
root-layout check looked in the same wrong place, and if the app's
routes were prerenderable the build passed too, so a repo the migration
never touched came out green.

On a dev server bound to another port, the preflight probe read
"unreachable" and refused to verify while `next dev` was running.

Both are silent failures, which is the worst case for instructions an
agent runs top to bottom.

### How?

- Anchor on `next.config.*` so an agent invoked from a subdirectory
doesn't test for `app/` against the wrong `cwd`.
- When `app/` and `src/app/` both exist, say so: Next.js builds `app/`
and never reads `src/app/`, so those routes are shadowed and unbuilt.
Ask which tree to migrate.
- Treat `0 ok` as a wrong path rather than a finished run.
- Move the `NEXT_MCP_URL` resolution into the `next-dev-loop` preflight.

The transforms are fine. Their path regexes match `src/app/...`, and
pointed at `./src/app` they convert every segment.
`remove-partial-prefetch` has the same shape and hardcoded path, so it's
covered here too.

Fixes #96649

---------

Co-authored-by: Claude Opus 5 <noreply@anthropic.com>
(cherry picked from commit 55ff2d2)

## Summary

- docs: remove experimental note from runtime prefetching (#96615)
- docs: proxy event argument (#96435)
- docs: correction to dynamicParams migration (#96624)
- docs: quote the dynamicParams build error in a blockquote (#96633)
- docs: use relative doc links in instant-navigation error pages
(#96672)
- docs: document ! exclusion and src/ prefix for --debug-build-paths
(#96703)
- docs: instant navigation quick start with an adoption prompt (#96663)
- docs (Skills): stop assuming app/ at the root and port 3000 (#96696)
- docs: present each Skill as steps in the AI agents guide (#96751)
- docs: update redirected links to current targets (#96723)
- docs: add authentication with Cache Components guide and iron-session
example (#95802)
- docs: link View Transitions skill on skills.sh and clarify the example
prompt (#96863)
- Add a `turbopackChunking` documentation page for pages router (#96698)
- docs: add `export const dynamic = 'force-static'` to Route Handlers
example on Static Exports (#96964)
- docs: runtime prefetching -> optimizing prefetching (#96934)
- Fix typo in Data Access Layer section (#87202)
- docs: rename repo to repository for consistency (#87849)
- docs(mdx): fix package name in .md handling section (#97131)
- docs: fix Link prefetch grammar and Client Components wording (#97132)
- docs: align Cache Components authentication guide title (#97143)
- docs: create client-side fetching guide (#96341)
- docs: clarify client cache freshness after hydration (#97180)
- docs: server client and directives (#96145)
- Update authentication diagram URL (#97320)
- docs: align SPA guide reducer example with React conventions (#97341)
- docs: app router reference accuracy (#97477)
- docs: mention Valibot as validation library option in forms guides
(#97468)
- docs: warn when catching permanentRedirect (#97496)
- [docs] fix: grammar typos in linking and navigating guide (#95544)
- docs: rename Vercel Edge Config to Global Config in redirecting guide
(#97456)
- docs: document metadata pagination field (#95509)
- docs: outlining and lcp (#96942)
- docs: adjust interactive app guide (#97558)
- docs: generateMetadata values should be serializable with use cache
(#97551)
- Fix stale cross-references in skills/ (#97566)
- Improve Cache Components sync IO migration guidance (#97572)
- docs: Explicit cache output description (#97548)
- docs: document deploymentId build ID override and Pages Router skew in
16.2 (#97645)
- docs: drop stale Route Handlers restriction from `use cache: private`
(docs part of #97349)
- docs: clarify beforeInteractive placement for root layouts (#97643)
- docs: Adapters entry page lists its children pages twice (#97677)
- docs: correct the upper stale bound for App Shell exclusion in
cacheLife (#97653)
- Improve Partial Prefetching adoption checks (#97637)
- docs: fix parallelRouteKey parameter name in
useSelectedLayoutSegment(s) (#97710)
- docs(adapters): document assetsHashes and routing.middlewareMatchers
(#96536)
- docs: note that response headers must be set before calling handle()
in a custom server (#97693)
- Document catchError for the Pages Router (#97748)
- docs: fix typos and correctness issues in App Router docs (#97823)
- docs: param access on use-server (#97865)
- docs: clarify revalidateTag profile expire semantics (#97836)

---------

Co-authored-by: Aurora Scharff <66901228+aurorascharff@users.noreply.github.com>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
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