JS-119: verb resolution must not depend on cwd/chdir — pin the jsrc climb root at session start

Now:: OPEN

Input

Context

RULING (gritzko, chat 2026-07-19, out of the [-N]-click investigation): which CODE a verb name resolves to must never depend on where the process happens to be chdir'd — capture the climb root ONCE at session start.

Today registry.js:66-67 verbFile(w, startDir) defaults dir = startDir || io.cwd() PER CALL, and loop.js invokes resolveVerb(w, undefined, …) — every cold verb require reads the live process cwd.
Currently benign only by accident: the pager never chdirs (row context rides loop.cli opts2.context as data, BE-039/BRO-024), so cwd == launch cwd for the whole session. Any future verb/editor leg that chdirs would silently re-root the climb into a FOREIGN tree's jsrc and mix that tree's code into the resident session.
Sibling defect from the same incident: a load-error from the resolved file is swallowed to "absent" — that mask is JS-074 (live-hit note added there), not this ticket.

Goals

The jsrc climb root is captured once at MAIN/session entry and threaded to every verbFile/resolveVerb call; a mid-session chdir changes NOTHING about verb resolution.

startDir stays as the explicit test/override hook.

Constraints

Behavior today is identical (cwd never moves) — this is hardening; no golden churn expected.
Root captured from the launch cwd's jsrc climb, not re-derived per call; keep verbFile's signature.

WIP

Design decisions

TODOs

red: fixture session resolves a verb, chdir into a second tree carrying a DIFFERENT jsrc verb of the same name, resolve again — must load the LAUNCH tree's code
capture the root at entry (be/loop init), thread through resolveVerb/verbFile default; green