🔧 Drop the redundant knip entry pattern

knip derives the public entry from package.json `exports` and resolves
it to src/index.ts itself, so naming the file in `entry` is redundant:
maintain:knip reported it as a configuration hint, and the scan is now
silent. Verified the barrel is still treated as the entry — the scope
is clean with and without dist/, and with src/index.test.ts removed.

Supersedes the workaround recorded in development/tooling.md, which
silenced an unused-file report for the barrel that the current entry
derivation no longer produces. Rewrite the section to state the
behaviour and keep the rejected `paths` mapping.

development/tooling.md

@@ -196,27 +196,28 @@ joining the oxfmt-superseded rules already off.
   are part of the public API.
 - The narrower scope keeps the signal high without config-file boilerplate.
 
-### `knip` lists `src/index.ts` as an entry
+### `knip` does not list the library entry
 
 #### Decision (2026-09)
 
-`knip.json` declares `"entry": ["src/index.ts", "scripts/*.ts"]`.
+`knip.json` declares `"entry": ["scripts/*.ts"]`; the library entry
+`src/index.ts` is not listed.
 
 #### Why
 
-- Supplying `entry` **replaces** knip's default entry detection, which otherwise
-  derives the public entry from `package.json` `exports`. Adding `scripts/*.ts`
-  there therefore dropped the library entry, so knip resolved the package through
-  its `dist/index.js` output and reported the unreferenced source entry file
-  `src/index.ts` as an unused file.
-- Naming the source entry restores the link between the public API and the
-  source graph without pointing knip at build output.
+- knip derives the public entry from `package.json` `exports` and resolves it to
+  `src/index.ts` itself, so naming the file is a redundant pattern and
+  `maintain:knip` reports it as a configuration hint.
+- Listing `scripts/*.ts` does not switch that derivation off: the scope stays
+  clean with or without `dist/`, and with the barrel's own test removed.
 
 #### Rejected
 
+- `"src/index.ts"` in `entry`: it silenced an `unused files` report for the
+  barrel, which the derivation above no longer produces; keeping it only adds a
+  hint.
 - `paths` mapping `dist/index.*` back to `src/index.ts`: more config to model a
-  relation the explicit entry states directly, and it would break whenever the
-  build layout changes.
+  relation knip already resolves.
 
 ### `maintain:outdated` ignores `@types/node`