BE-022 MED: be/ helper duplication sweep — re-implemented reads, tip-peeks, constants, decoders

Landed refactors (JSQUE-016 reorg, URI-013 cleanup) left copy-sites that should call the shared helper; several have already DRIFTED. One sweep, each site listed:

verbs/head/head.js:120 + :203 — the cached-remote-tip peek (eachRemote match + stripLeadRef) is duplicated VERBATIM from get.js, with DIVERGENT error vocabulary (HIGH-ish: two codes for one refusal).
verbs/get/get.js:130 — oldTipOf re-implements the wtlog tip read and MISSES detached ?<sha> rows.
shared/wire.js:545 — ZERO_SHA tombstone constant defined THREE times; util/sha.js owns the zero-sha concept.
views/bro/pager.js:228 — re-implements spell.js helpers it ALREADY imports (joinPath verbatim, dirOf/dirOfPath, an inline dirname).
views/status/status.js:423 — re-implements isMount WITHOUT recurse.js's GET-036 symlink guard (and duplicates joinPrefix).
views/cat/cat.js:104 — readFileBytes re-implemented in cat.js and spot/search.js despite wtread.js being "the ONE reg-file wt read".
shared/wtread.js:10 — io.readAll called with a 3rd size arg the binding SILENTLY IGNORES — wrong contract encoded at 5 sites.
shared/serve.js:45 — inline branch→refs/heads mapping instead of relate.resolveRef, DROPPING its guards.
core/loop.js:180 — TRANSPORT map duplicates SCHEME_ALLOW's transports (loop.js:27); pager.js:241 already drifted (missing keeper).

From the 2026-07-07 be/ review (BE/REVIEW), all CONFIRMED. Method Issues.

Input

Context

Each copy is a place a future fix lands in one site and misses the other(s); the pager/keeper and head/get error-vocab drifts already happened.
Shared owners exist: shared/util/path.js, util/sha.js, shared/wtread.js, shared/spell.js, core/recurse.js isMount, relate.resolveRef.

Goals

Each site calls the shared helper; one TRANSPORTS constant seeds SCHEME_ALLOW + TRANSPORT + pager; head/get share one tip-peek with one error code; ZERO_SHA single-sourced; wtread readAll called with the real 2-arg contract.

Constraints

Pure refactor — behavior-preserving except the fixed drift (detached-row tip read, keeper transport, GET-036 symlink guard now applied in status). Suite byte-stable where output is asserted.

WIP

Design decisions

(pending)

TODOs

Consolidate each listed site onto its shared owner; suite green.

Blockers and bummers

status isMount adopting recurse.js's guard changes nested-mount output — cross-check against GET-036.

Outcome

(pending)