Fix incorrect vendored detections (#36508)

Fixes: https://github.com/go-gitea/gitea/issues/22618

`go-enry`'s `IsVendor` function marks git paths (`.gitignore`,
`.gitattributes`, `.gitmodules`), github/gitea paths (`.github/`,
`.gitea/`) as "vendored" for GitHub Linguist language statistics. This
causes these files to incorrectly display the "Vendored" tag in diff
views.

Override `go-enry`'s detection for these specific cases while preserving
its behavior for actual vendor directories.

---------

Signed-off-by: silverwind <me@silverwind.io>
Signed-off-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: silverwind <115237+silverwind@users.noreply.github.com>
Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

AGENTS.md

@@ -1,7 +1,10 @@
 # Instructions for agents
 
 - Use `make help` to find available development targets
-- Before committing go code changes, run `make fmt`
+- Use the latest Golang stable release when working on Go code
+- Use the latest Node.js LTS release when working on TypeScript code
+- Before committing `.go` changes, run `make fmt` to format, and run `make lint-go` to lint
+- Before committing `.ts` changes, run `make lint-js` to lint
 - Before committing `go.mod` changes, run `make tidy`
 - Before committing new `.go` files, add the current year into the copyright header
-- Before committing files, removed any trailing whitespace
+- Before committing any files, remove all trailing whitespace from source code lines