refactor: drop the URL-based error classifier and hint lookups

Errors are named by the service call that failed: Classify,
NotFoundError and ConflictError at the call site. Remove the endpoint
parser that guessed the resource from the request path, and the
follow-up reads the explainer made at error time (repository state,
issue-vs-pull-request, the existing pull request's URL) together with
the credentialed transport each API error carried for them.

Calls that the endpoint parser covered and the services did not now
classify themselves: issues, pull requests, reviews, comments,
releases, branches, wiki pages, repositories, organizations and SSH
keys. Unclassified failures fall back to the generic
"not found (HTTP 404 GET ...)" text.

Signed-off-by: bircni <bircni@icloud.com>

internal/app/ssh_keys.go

@@ -174,7 +174,7 @@ $ cat key.pub | tea ssh-key add`,
 			service := services.SSHKeys{Client: target.client}
 			created, err := service.Create(cmd.Context(), title, strings.TrimSpace(string(data)))
 			if err != nil {
-				return a.registeredKey(cmd.Context(), service, key, services.ClassifyRequest(err))
+				return a.registeredKey(cmd.Context(), service, key, err)
 			}
 			a.done(cmd, "Added %s", sshKeyLabel(created))
 			return a.jsonResult(cmd, created)