fix(lint): godoc comment on NewAuthWithNamedKeys must lead with function name (ST1020)

CI failure on master (commit 3287e17) — staticcheck ST1020:

  internal/api/middleware/middleware.go:125:1: ST1020: comment on exported
  function NewAuthWithNamedKeys should be of the form
  "NewAuthWithNamedKeys ..." (staticcheck)

When NewAuth was renamed to NewAuthWithNamedKeys during the M-002 auth
unification, the leading godoc sentence was left pointing at the old name.
Rewrite the comment so its first sentence starts with the new function
name, and expand the body to describe the named-key + admin-flag contract
introduced in 3287e17.

Also gitignore /.gopath/ — session-scoped tool install cache, same
category as /.gocache/ and /.gomodcache/.

Verification:
  go vet ./internal/api/middleware/...          — clean
  go build ./internal/api/middleware/...        — clean
  go test ./internal/api/middleware/...         — PASS (0.245s)
  staticcheck -checks=all,<project exclusions>  — clean across
    middleware, handler, service, domain, cmd/server, scheduler

Closes: CI failure on 3287e17.

internal/api/middleware/middleware.go

@@ -122,10 +122,15 @@ type AuthConfig struct {
 	Secret string // The raw API key or comma-separated list of valid API keys
 }
 
-// NewAuth creates an authentication middleware based on config.
-// When Type is "none", all requests pass through (demo/development mode).
-// When Type is "api-key", requests must include a valid Bearer token.
-// Named keys are supported via []NamedAPIKey input.
+// NewAuthWithNamedKeys creates an authentication middleware that validates
+// Bearer tokens against a set of named API keys. Each key carries a name
+// (propagated as the actor via context) and an admin flag (consulted by
+// authorization gates such as bulk revocation).
+//
+// When namedKeys is empty the returned middleware is a no-op pass-through,
+// which is used in demo/development mode (CERTCTL_AUTH_TYPE=none). When one
+// or more keys are provided, requests must include a matching Bearer token
+// or they are rejected with 401.
 func NewAuthWithNamedKeys(namedKeys []NamedAPIKey) func(http.Handler) http.Handler {
 	if len(namedKeys) == 0 {
 		return func(next http.Handler) http.Handler {