Let the login sheet respect its edges and the account footer tell the truth

MAC2/MAC15: the macOS login form is grouped like its Edit Source parent, so
labels sit inside the sheet and the add-flow step stops clipping; footers
wrap instead of truncating.
MAC12: the account section footer consults account statuses before claiming
the user is logged in.

Yattee/Views/Settings/InstanceAccountsSection.swift

@@ -77,7 +77,7 @@ struct InstanceAccountsSection: View {
         } header: {
             Text(String(localized: "login.header.account"))
         } footer: {
-            Text(String(localized: accounts.isEmpty ? "login.footer.loginBenefits" : "login.footer.loggedIn"))
+            Text(footerText)
         }
         .onReceive(NotificationCenter.default.publisher(for: .accountCredentialDidChange)) { _ in
             credentialRevision &+= 1
@@ -216,6 +216,45 @@ struct InstanceAccountsSection: View {
 
     // MARK: - Presentation
 
+    /// What the section says under the rows.
+    ///
+    /// Read from the statuses, not from the count: this is the screen the user
+    /// comes to in order to fix a login the server turned down, and a footer
+    /// that only counts accounts tells them, right there, that they are logged
+    /// in. The worst state on the list is the one that gets named — a rejected
+    /// credential is something to act on, and it outranks a server that
+    /// happens to be down.
+    private var footerText: String {
+        guard !accounts.isEmpty else {
+            return String(localized: "login.footer.loginBenefits")
+        }
+
+        // `checking` counts as healthy: it is the absence of an answer, and a
+        // footer that reacted to it would blink a warning at every launch.
+        let unhealthy = accounts.map { status(for: $0) }
+            .filter { $0 != .signedIn && $0 != .checking }
+
+        guard !unhealthy.isEmpty else {
+            return String(localized: "login.footer.loggedIn")
+        }
+
+        if unhealthy.contains(.credentialRejected) {
+            return String(localized: "login.footer.credentialRejected")
+        }
+
+        if unhealthy.contains(.unreachable) {
+            return String(localized: "login.footer.unreachable")
+        }
+
+        if unhealthy.contains(.credentialMissing) {
+            return String(localized: "login.footer.credentialMissing")
+        }
+
+        // A state named after this was written. Saying only that something is
+        // wrong is worth little, but it is true, and the rows above say what.
+        return String(localized: "login.footer.accountUnusable")
+    }
+
     private func displayName(for account: Account) -> String {
         appEnvironment?.dataContextValidator.displayName(for: account) ?? instance.displayName
     }

Yattee/Views/Settings/InstanceLoginView.swift

@@ -73,7 +73,12 @@ struct InstanceLoginView: View {
                 .accessibilityIdentifier("instance.login.view")
         }
         #if os(macOS)
-        .frame(minWidth: 450, minHeight: 350)
+        // Sized to what the form actually holds: two fields and a button leave
+        // most of a taller sheet empty, and the optional step carries two more
+        // rows than the plain one. The width is what the labels have to fit
+        // in, which matters most where this is pushed on top of the add flow's
+        // own sheet.
+        .frame(minWidth: 480, minHeight: isOptionalStep ? 400 : 300)
         #endif
         #endif
     }
@@ -84,6 +89,19 @@ struct InstanceLoginView: View {
                 #if os(tvOS)
                 TVSettingsTextField(title: usernameFieldLabel, text: $username)
                 TVSettingsTextField(title: String(localized: "login.password"), text: $password, isSecure: true)
+                #elseif os(macOS)
+                LabeledContent(usernameFieldLabel) {
+                    TextField("", text: $username)
+                        .textContentType(.username)
+                        .autocorrectionDisabled()
+                        .accessibilityIdentifier("instance.login.usernameField")
+                }
+
+                LabeledContent(String(localized: "login.password")) {
+                    SecureField("", text: $password)
+                        .textContentType(.password)
+                        .accessibilityIdentifier("instance.login.passwordField")
+                }
                 #else
                 TextField(usernameFieldLabel, text: $username)
                     .textContentType(.username)
@@ -100,7 +118,7 @@ struct InstanceLoginView: View {
             } header: {
                 Text(String(localized: "login.header.credentials"))
             } footer: {
-                Text(footerText)
+                wrappingFooter(footerText)
             }
 
             if let error = errorMessage {
@@ -144,13 +162,17 @@ struct InstanceLoginView: View {
                     .buttonStyle(TVSettingsButtonStyle())
                     #endif
                 } footer: {
-                    Text(String(localized: "login.footer.optionalStep"))
+                    wrappingFooter(String(localized: "login.footer.optionalStep"))
                 }
             }
         }
         #if os(iOS)
         .scrollDismissesKeyboard(.interactively)
         #endif
+        #if os(macOS)
+        .formStyle(.grouped)
+        .opaqueSettingsFormBackground()
+        #endif
         .onAppear {
             // Only ever fills an untouched field: the sheet's body runs again
             // for every keystroke, and a prefill that reasserted itself would
@@ -163,6 +185,17 @@ struct InstanceLoginView: View {
 
     // MARK: - Computed Properties
 
+    /// A section footer that takes as many lines as it needs.
+    ///
+    /// The sentences here explain what the form is for and that skipping it is
+    /// safe, and the sheet is narrow — narrower still when it is pushed on top
+    /// of the add flow's sheet. Left to lay itself out, macOS keeps the footer
+    /// on one line and cuts the end of it off.
+    private func wrappingFooter(_ text: String) -> some View {
+        Text(text)
+            .fixedSize(horizontal: false, vertical: true)
+    }
+
     /// What the first field is called on this backend.
     ///
     /// Named per backend rather than genericised: every backend that has