UI: A axis surface (DRO row, jog, Home A, settings page)

Front-end side of the gplan-integrated A axis (B3).

- a-axis-view.{js,pug}: dedicated settings page that mounts the
  AAxisSettings Svelte component and lives at #a-axis in the V09
  settings rail.
- AAxisSettings.svelte: aux.json-backed form (axis letter, port,
  homing direction, soft limits, ATC pin map, etc.) with master
  Save integration via 'onefin:save-all'.
- main.ts + SettingsView.svelte: register AAxisSettings in the
  Svelte component map; SettingsView no longer embeds the W axis
  fieldset.
- settings-shell-view: 'A Axis' rail entry; route to a-axis-view.
- app.js: extend settings family to include 'a-axis'; broadcast
  onefin:save-all from the master Save button.
- control-view: Home All button waits for the gantry cycle to
  finish before firing Home A on a non-virtual setup; A jog
  buttons; aux_jog/aux_home/aux_jog_incr methods.
- control-view.pug: A row in the DRO (with set-position + zero +
  home actions), A- / A+ tiles in the jog grid (gated on
  w.enabled || a.enabled), legacy W row kept for installs that
  haven't migrated to the gplan integration.
- style.styl: dro-axis.axis-w color.

src/js/settings-shell-view.js

@@ -24,6 +24,7 @@ module.exports = {
     "io-view":                 require("./io-view"),
     "macros-view":             require("./macros"),
     "help-view":               require("./help-view"),
+    "a-axis-view":             require("./a-axis-view"),
     "cheat-sheet-view": {
       template: "#cheat-sheet-view-template",
       data: function () {
@@ -56,6 +57,9 @@ module.exports = {
         { sub: "motor", motor: 1, href: "#motor:1", icon: "fa-arrows-up-down-left-right", label: "Motor 1" },
         { sub: "motor", motor: 2, href: "#motor:2", icon: "fa-arrows-up-down-left-right", label: "Motor 2" },
         { sub: "motor", motor: 3, href: "#motor:3", icon: "fa-arrows-up-down-left-right", label: "Motor 3" },
+        // Auxiliary axis (auxcnc ESP32 - exposed to gplan as A).
+        // Mounts the AAxisSettings Svelte component on its own page.
+        { sub: "a-axis", href: "#a-axis", icon: "fa-arrows-up-down", label: "A Axis" },
         { section: " " },
         { sub: "help",           href: "#help",           icon: "fa-circle-question", label: "Help" },
       ],
@@ -133,6 +137,7 @@ module.exports = {
         // layout, which under tablet mode pulls the fixed header out
         // of view.
         if (location.hash !== item.href) location.hash = item.href;
+        this._a_axis_focus = (item.sub === "a-axis");
         const reset = () => {
           // Force any inadvertent ancestor scroll back to 0 before
           // we move .settings-content explicitly.
@@ -155,6 +160,7 @@ module.exports = {
           requestAnimationFrame(reset);
         }, 320);
       } else {
+        this._a_axis_focus = false;
         if (location.hash !== item.href) location.hash = item.href;
         // Reset .app-body scroll so each route starts at the top.
         const body = document.querySelector(".app-body");