docs: split README into overview and operator guide for release

Co-authored-by: Cursor <cursoragent@cursor.com>

test/e2e/negative_test.go

@@ -195,7 +195,7 @@ func testSessionSurvivesRestart(t *testing.T, sc *scenario) {
 }
 
 // testLevel1RateLimit is plan C.4 negative check 4: the native Postfix anvil
-// backstop (smtpd_client_message_rate_limit, README § Rate limiting), set by
+// backstop (smtpd_client_message_rate_limit, guide § Rate limiting), set by
 // the override to RATE_LIMIT_MESSAGES_PER_IP=50, rejects once exceeded. It
 // uses a dedicated application with no level-2 limit of its own, and retries
 // well past that count, so the result is unambiguous regardless of how much of

test/e2e/panel_client.go

@@ -170,7 +170,7 @@ func (c *panelClient) addApplication(domainID, login, mode, addresses string) (a
 	return appLogin, password, nil
 }
 
-// setRateLimit saves a level-2 differentiated limit (README § Rate limiting)
+// setRateLimit saves a level-2 differentiated limit (guide § Rate limiting)
 // on either a domain (/domains/{id}/ratelimit) or an application
 // (/applications/{id}/ratelimit).
 func (c *panelClient) setRateLimit(path, allowedIP string, maxMessages, windowSeconds int) error {