feedback7 R22-GHSIM: 假想敌：骨刺 changes model with its 隐匿 at once — the three-headed snake (*_A) while hidden, its *_B set when blocked or revealed, back to *_A when hidden again (GitHub #296, PR #365 by @Sukvii, render part); golden: unchanged

The contributor's code (render/spine.js syncFormPose, the render/units.js wiring and FORMS entry, the headless
test/render/forms.test.js block), applied from PR #365, so they are the author of this commit. Maintainer side: the
hard-coded Spine id became a STEALTH_FORMS table (form while the stealth bit is off), comments and docs/ASSETS.md
reworded. Not ported: the PR's sim targeting rewrite (content/enemies/invisible.js), its enemies_bosses tests, its
roster.json and the Chrome suite (forms.browser.test.js, not run here).

Seen (#296, FrogThai): a blocked 骨刺 kept the snake. The sim already sends UF.STEALTH only while its 隐匿 is effective
(not blocked, not revealed — targeting.js enemyStealthed); the view now keys the FORMS 'revealed' clip set (Idle_B /
Move_B / Die_B / Attack_B, all in the skeleton) off that bit in UnitView.sync — before a DIE of the same snapshot — and
re-poses at once: a running attack continues in the other attack clip at the same point relative to its strike frame
(Attack_A hit 0.533 s, Attack_B 0.733 s; a pending wind-up still strikes on time), a stun / idle restarts on the new set
without a crossfade, and a frozen skeleton is posed with update(0); a model loaded later is posed the same way.
Golden: unchanged (render only).

public/js/render/spine.js

@@ -200,6 +200,41 @@ export class SpineActor {
     else if (this.mode === 'stun' && this.has(this.roles.stun?.loop)) this._play(this.roles.stun.loop, true);
   }
 
+  /**
+   * Re-pose on the clip set in force right after an immediate form switch (render/units.js STEALTH_FORMS: 假想敌：骨刺's
+   * stealth bit; PR #365): a running attack goes on in the new set's attack clip at the same point relative to its
+   * strike frame (a pending wind-up still strikes at windUntil), a stun / the resting state restarts on the new set's
+   * clip without a crossfade, and the skeleton is posed at once — also while a freeze holds it (`frozen`).
+   */
+  syncFormPose() {
+    if (this.dead) return;
+    if (this.mode === 'attack') {
+      const track = this.spine.state.tracks[0];
+      const clip = this._attackClip();
+      if (!track || !clip) return;
+      const dur = this.dur(clip.loop);
+      const oldHit = this._hitTime(this.current, this.dur(this.current));
+      const hit = this._hitTime(clip.loop, dur);
+      const start = clampN(track.trackTime + hit - oldHit, 0, dur);
+      const lead = this.wound && this.windUntil != null
+        ? Math.max(0, this.windUntil - this.clock) : 0;
+      const ts = lead > 0 ? Math.max(0, hit - start) / lead : track.timeScale;
+      const tailTs = lead > 0 ? this.windTs : ts;
+      this._play(clip.loop, track.loop, { start, timeScale: ts, mix: 0 });
+      this.attackUntil = this.clock + lead +
+        Math.max(0, dur - (lead > 0 ? hit : start)) / tailTs;
+    } else if (this.mode === 'stun') {
+      const name = this.has(this.roles.stun?.loop) ? this.roles.stun.loop : this._baseName();
+      this._play(name, true, { mix: 0 });
+    } else if (this.mode === 'base') {
+      this._play(this._baseName(), true, { mix: 0 });
+    } else {
+      return;
+    }
+    // Apply the new attachments even when normal updates are frozen.
+    this.spine.update(0);
+  }
+
   /** Play a form's transition clip once; attacks and the resting state wait for it (mode 'change'). */
   _change(clip) {
     if (this.mode !== 'change') this.stunWanted = this.mode === 'stun';