perf: pre-compile hot-path JS expressions in QuickJS Init()

[zeroedin]

Description

CallHook calls Eval("__hooks[__callHookName](__callInput)") per page per hook — parsing and compiling the same JS expression 820+ times per hook invocation. setPayloadFrontMatter and setPayloadTOC each call Eval("Object.defineProperty(...)") per page for the lazy getter setup.

Eval lexes, parses, and compiles the source string on every call. For a static expression called 820 times, that's 819 redundant compilations.

Fix

Pre-compile static expressions as named functions during Init():

function __callHookByName(name, input) {
  return __hooks[name](input);
}
function __installLazyFM(target, jsonStr) {
  Object.defineProperty(target, 'frontMatter', { get: ..., set: ..., configurable: true });
}
function __installLazyTOC(target, jsonStr) {
  Object.defineProperty(target, 'toc', { get: ..., set: ..., configurable: true });
}

Call via InvokeJS("__callHookByName", nameVal, input) instead of Eval(...). InvokeJS calls the pre-compiled function directly — no parse, no compile.

Measured impact

820-page RHDS benchmark: ~200ms reduction in post-render hooks. Small individually, but it compounds with the other fast-path optimizations.

Scope

• Add the three functions to the alloy-setup.js eval block in Init()
• Replace Eval calls in invokeHookFastPath, setPayloadFrontMatter, setPayloadTOC with InvokeJS
• Applies the same principle from dev-advice.md fix: consolidate config defaults into single source of truth #21: never Eval a static expression inside a loop

Refs #1185, #1180