Podcast player: pause no longer kills the system voice

"It only plays once, and when you pause it you can't unpause."

WebKit leaves speechSynthesis paused after a cancel(), and every later
speak() is queued into that paused state - silently. Fixes:
- resume() whenever the synth is paused, before speaking and after our own
  cancel;
- a ~90ms beat before a speak() that follows a cancel (several engines drop
  it otherwise);
- no cancel when nothing is pending.

The speech engine also no longer rebuilds on rate or voice changes: both are
read live through getters, so a voiceschanged arriving after the first
utterance cannot leave a second engine speaking over the first. A rate or
voice change restarts the current part from the same word instead (the Web
Speech API cannot change either mid-utterance), making the change audible at
once; the natural engine applies speed live and resumes across a voice swap.

The suite's speech stub now models the quirk (cancel -> paused, speak while
paused is dropped and counted) and pins that nothing is ever spoken into a
paused engine. 44 checks. Version 0.7.7, SW v99.

public/sw.js

@@ -9,7 +9,7 @@
  *
  * Bumping CACHE_VERSION is how a new deploy invalidates old assets.
  */
-const CACHE_VERSION = "freezmo-v98";
+const CACHE_VERSION = "freezmo-v99";
 const SHELL_CACHE = `${CACHE_VERSION}-shell`;
 const ASSET_CACHE = `${CACHE_VERSION}-assets`;