feat(userscript): 25s dwell before auto-update + draggable edge-snap FAB

Auto-update no longer fires the instant a newer chapter opens (guards against
a misclick on "latest chapter"). Instead a 25s dwell timer arms, shown by a
countdown ring filling around the FAB; the manual "Update to X" button still
fires immediately. Timer is keyed to the chapter, not the URL, so turning
pages within the same chapter (Demonic /chapter/N/<page>) keeps it counting
rather than resetting.

FAB is now draggable: drag anywhere, release snaps it to the nearer left/right
edge keeping its vertical position, persisted in localStorage across sessions
and re-clamped on rotation. A drag no longer opens the panel; a tap still does.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

userscript/manga-bookmark.user.js

@@ -1,7 +1,7 @@
 // ==UserScript==
 // @name         Manga Bookmark Sync
 // @namespace    mangabm
-// @version      1.0.0
+// @version      1.1.0
 // @description  Track read progress on Asura & Demonic and sync to a self-hosted backend. Bromite-compatible (no GM_* APIs).
 // @author       you
 // @match        https://asuracomic.net/*
@@ -259,6 +259,7 @@
   }
 
   async function updateToCurrentChapter() {
+    cancelDwell(); // manual button + timer-fire both clear any pending dwell
     const p = state.page;
     if (p.type !== "chapter") return;
     const key = keyOf(p);
@@ -315,9 +316,42 @@
     }
   }
 
-  // Auto-record on opening a chapter of a bookmarked series.
+  // Dwell timer: don't advance progress the instant a newer chapter opens (guards
-  async function maybeAutoUpdate() {
+  // against a misclick on "latest chapter"). Arm a 25s timer instead; the countdown
+  // ring around the FAB shows it running. The manual "Update to X" button still fires
+  // immediately. Timer is keyed to the chapter, not the URL, so turning pages within
+  // the same chapter (Demonic /chapter/N/<page>) keeps it counting rather than resetting.
+  const DWELL_MS = 25000;
+  let dwell = null; // { id, timerId }
+
+  function chapterIdentity(p) {
+    return p && p.type === "chapter" ? p.site + ":" + p.seriesId + "@" + p.chapterNum : null;
+  }
+
+  function armDwell(id) {
+    dwell = {
+      id,
+      timerId: setTimeout(() => {
+        dwell = null;
+        stopRing();
+        updateToCurrentChapter();
+      }, DWELL_MS),
+    };
+    startRing(DWELL_MS);
+  }
+
+  function cancelDwell() {
+    if (dwell) clearTimeout(dwell.timerId);
+    dwell = null;
+    stopRing();
+  }
+
+  // Auto-record on opening a chapter of a bookmarked series (after the dwell delay).
+  function maybeAutoUpdate() {
     const p = state.page;
+    const id = chapterIdentity(p);
+    if (dwell && id === dwell.id) return; // same chapter, page turn — keep timer running
+    cancelDwell(); // navigated elsewhere — drop any stale dwell
     if (p.type !== "chapter") return;
     const existing = state.byKey[keyOf(p)];
     if (!existing) return; // only track series the user bookmarked
@@ -330,7 +364,7 @@
     if (existing.last_chapter_url === p.chapterUrl && existing.last_chapter === p.chapterLabel) {
       return; // already recorded
     }
-    await updateToCurrentChapter();
+    armDwell(id);
   }
 
   // ============================================================
@@ -355,9 +389,136 @@
     wrap.innerHTML = TEMPLATE;
     root.appendChild(wrap);
 
-    root.getElementById("fab").addEventListener("click", togglePanel);
+    const fab = root.getElementById("fab");
+    fab.addEventListener("click", () => {
+      if (fab.dataset.dragged) {
+        delete fab.dataset.dragged; // this click is the tail of a drag — swallow it
+        return;
+      }
+      togglePanel();
+    });
     root.getElementById("backdrop").addEventListener("click", togglePanel);
     root.getElementById("closeBtn").addEventListener("click", togglePanel);
+
+    placeFab(fab);
+    makeDraggable(fab);
+    window.addEventListener("resize", () => placeFab(fab)); // re-clamp on rotation
+  }
+
+  // ============================================================
+  // FAB placement + dragging (snaps to nearest left/right edge)
+  // ============================================================
+
+  const FAB_KEY = "mangabm:fabpos";
+  const FAB_MARGIN = 12;
+
+  function clamp(v, lo, hi) {
+    return Math.max(lo, Math.min(hi, v));
+  }
+
+  function applyFabPos(fab, side, y) {
+    fab.style.top = y + "px";
+    fab.style.bottom = "auto";
+    if (side === "left") {
+      fab.style.left = FAB_MARGIN + "px";
+      fab.style.right = "auto";
+    } else {
+      fab.style.right = FAB_MARGIN + "px";
+      fab.style.left = "auto";
+    }
+  }
+
+  function loadFabPos() {
+    try {
+      return JSON.parse(localStorage.getItem(FAB_KEY));
+    } catch (e) {
+      return null;
+    }
+  }
+
+  function saveFabPos(side, yRatio) {
+    try {
+      localStorage.setItem(FAB_KEY, JSON.stringify({ side, yRatio }));
+    } catch (e) {
+      /* quota / private mode — ignore */
+    }
+  }
+
+  function placeFab(fab) {
+    const s = fab.offsetWidth || 52;
+    const p = loadFabPos();
+    const maxY = window.innerHeight - s - FAB_MARGIN;
+    const side = p && p.side === "left" ? "left" : "right";
+    const y = p ? clamp(p.yRatio * window.innerHeight, FAB_MARGIN, maxY) : maxY - 8;
+    applyFabPos(fab, side, y);
+  }
+
+  function makeDraggable(fab) {
+    let down = false, moved = false, sx = 0, sy = 0, offX = 0, offY = 0;
+    fab.addEventListener("pointerdown", (e) => {
+      down = true;
+      moved = false;
+      sx = e.clientX;
+      sy = e.clientY;
+      const r = fab.getBoundingClientRect();
+      offX = e.clientX - r.left;
+      offY = e.clientY - r.top;
+      fab.setPointerCapture(e.pointerId);
+      fab.style.transition = "none";
+    });
+    fab.addEventListener("pointermove", (e) => {
+      if (!down) return;
+      if (!moved && (Math.abs(e.clientX - sx) > 6 || Math.abs(e.clientY - sy) > 6)) moved = true;
+      if (!moved) return;
+      e.preventDefault();
+      const s = fab.offsetWidth;
+      fab.style.left = clamp(e.clientX - offX, 0, window.innerWidth - s) + "px";
+      fab.style.right = "auto";
+      fab.style.top = clamp(e.clientY - offY, 0, window.innerHeight - s) + "px";
+      fab.style.bottom = "auto";
+    });
+    fab.addEventListener("pointerup", (e) => {
+      if (!down) return;
+      down = false;
+      fab.style.transition = "";
+      if (!moved) return; // tap — let the click handler toggle the panel
+      fab.dataset.dragged = "1"; // suppress the click that trails this drag
+      const s = fab.offsetWidth;
+      const r = fab.getBoundingClientRect();
+      const side = r.left + s / 2 < window.innerWidth / 2 ? "left" : "right";
+      const y = clamp(r.top, FAB_MARGIN, window.innerHeight - s - FAB_MARGIN);
+      fab.style.transition = "left .2s ease, right .2s ease, top .2s ease";
+      applyFabPos(fab, side, y);
+      saveFabPos(side, y / window.innerHeight);
+    });
+  }
+
+  // ============================================================
+  // Countdown ring around the FAB (dwell-timer progress)
+  // ============================================================
+
+  const RING_C = 144.5; // circumference: 2π·23
+
+  function startRing(ms) {
+    if (!root) return;
+    const ring = root.getElementById("ring");
+    const prog = ring.firstElementChild;
+    ring.classList.add("active");
+    prog.style.transition = "none";
+    prog.style.strokeDashoffset = RING_C; // empty
+    prog.getBoundingClientRect(); // reflow so the next assignment animates
+    prog.style.transition = "stroke-dashoffset " + ms + "ms linear";
+    prog.style.strokeDashoffset = "0"; // fills over ms
+  }
+
+  function stopRing() {
+    if (!root) return;
+    const ring = root.getElementById("ring");
+    if (!ring) return;
+    const prog = ring.firstElementChild;
+    ring.classList.remove("active");
+    prog.style.transition = "none";
+    prog.style.strokeDashoffset = RING_C;
   }
 
   function togglePanel() {
@@ -516,7 +677,10 @@
   // ============================================================
 
   const TEMPLATE = `
-    <button id="fab" aria-label="Manga bookmarks">📑</button>
+    <button id="fab" aria-label="Manga bookmarks">
+      <svg id="ring" viewBox="0 0 52 52" aria-hidden="true"><circle class="prog" cx="26" cy="26" r="23"></circle></svg>
+      <span class="fab-icon">📑</span>
+    </button>
     <div id="backdrop"></div>
     <aside id="panel" role="dialog" aria-label="Manga bookmarks">
       <header>
@@ -533,13 +697,24 @@
     :host { all: initial; }
     * { box-sizing: border-box; font-family: system-ui, -apple-system, sans-serif; }
     #fab {
-      position: fixed; right: 16px;
+      position: fixed;
-      bottom: calc(16px + env(safe-area-inset-bottom, 0px));
       width: 52px; height: 52px; border-radius: 50%; border: none;
-      background: #6d28d9; color: #fff; font-size: 22px; line-height: 52px;
+      background: #6d28d9; color: #fff; font-size: 22px;
       box-shadow: 0 4px 14px rgba(0,0,0,.4); z-index: 2147483646; cursor: pointer;
+      touch-action: none; user-select: none;
+      display: flex; align-items: center; justify-content: center; padding: 0;
     }
     #fab:active { transform: scale(.94); }
+    #ring {
+      position: absolute; inset: 0; transform: rotate(-90deg);
+      opacity: 0; transition: opacity .15s; pointer-events: none;
+    }
+    #ring.active { opacity: 1; }
+    #ring .prog {
+      fill: none; stroke: #c4b5fd; stroke-width: 3; stroke-linecap: round;
+      stroke-dasharray: 144.5; stroke-dashoffset: 144.5;
+    }
+    .fab-icon { position: relative; z-index: 1; line-height: 1; }
     #backdrop {
       position: fixed; inset: 0; background: rgba(0,0,0,.5);
       opacity: 0; pointer-events: none; transition: opacity .2s; z-index: 2147483646;