DOG-022: promote spot/RXLITS into dog/tok + jab tok._rx_lits binding

Now
OPEN

Input

Context

RXLITS (regex literal runs, the Russ Cox trigram-filter feed) sits in beagle/spot/RXLITS.c.rl but is another grammar for dog/tok by nature: a self-contained ragel machine over pattern bytes, depending on abc/INT.h only. /todo/SPOT/SPOT-003's JS regex filter needs it, and jab links only the dog submodule + abc-core spot's C is out of reach from JS land; hand-parsing regex in JS is banned.

Goals

Move the machine into the dog submodule and expose it to JS.

Constraints

WIP

Design decisions

TODOs

Blockers and bummers

Outcome

(pending)