Add /impeccable generate: agent-initiated live variants (Node-era squash)

Squash of the ten commits reviewed on PR #626, plus the last review
round's connection-aware roll call, before the rebase onto the Rust
engine: the generate command reference and router row, the overlay's
agent-target handling (roll call, leases, replay, rescue), the Node-era
live-server routes and live-generate CLI, the hook stand-down, the pricing
cards e2e fixture, and the unit, contract, e2e, and skill-behavior tests.
The server, CLI, hook, and pin halves are ported to the engine crates in
the commits that follow.

AI-assisted: implemented and tested with Claude Code under maintainer
direction.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

scripts/lib/skill-categories.js

@@ -37,6 +37,7 @@ export const SKILL_CATEGORIES = {
   document: 'system',
   extract: 'system',
   live: 'system',
+  generate: 'system',
 };
 
 export const CATEGORY_ORDER = ['create', 'evaluate', 'refine', 'simplify', 'harden', 'system'];