JS-030 MED: `bin/lib/keeper.js` — JS keeper-store reader (libdog+abc)

Read keeper objects/refs/trees in pure JS over git.pack + abc.index + ULOG — no keeper dog linked. Part of JS-027. Method: Issues.

Input

Context

Keeper store = NNNNN.keeper pack-logs (git.pack) + .idx wh128 LSM
(abc.index) + refs ULOG. So object/ref/tree read is reimplementable in JS, sharing zero code with the keeper dog.

Goals

getObject(sha) -> {type, bytes} (idx lookup → pack seek → inflate → delta chase).
resolveRef(?branch) -> sha, eachTip(cb), eachRemote(cb) over the refs ULOG.
readTree(sha) (via JS-028 git.tree), commitTree(sha)/commitParents(sha)
(via JS-028 git.parseCommit).

Constraints

libdog+abc ONLY. Map pack-logs via git.pack.mmap; wh128 lookup via abc.index.
Read-only; shard located via JS-029 be.js.

WIP

Design decisions

v1 read-only, no write path. Cache opened pack-logs per shard within a run.

TODOs

Repro-first (test/bin/): getObject of a known commit/tree/blob sha re-hashes
to that sha (codec.sha1); resolveRef('?') == trunk tip; readTree entry set vs a fixture; commitParents vs be log:.
Build over JS-028 + JS-029; smoke against the live repo.

Blockers

← JS-028, JS-029.

Outcome

(pending)