fix(keys): gate the test override behind NODE_ENV so a prod server can never honor it

Review fold-in. The reviewer landed the sharpest possible critique: the first cut closed a
test-hygiene hole by opening a quieter AUTH-CORRECTNESS one, and its only guard against that
was "the variable has an awkward name" — a naming convention plus a comment. That is precisely
the failure mode this whole PR exists to indict (a comment describing an intention that nothing
enforces). It was demonstrated live:

    OCP_DIR_OVERRIDE=/tmp/evil-store  ->  server opens /tmp/evil-store/ocp.db, 0 keys visible

server.mjs imports keys.mjs, and `ocp start`'s nohup fallback inherits the invoking shell's env
— so a maintainer who exported the var while debugging THIS issue and then started the server
would get a server silently authenticating against an empty key store. In AUTH_MODE=multi that
is a total auth outage: every real key 401s, nothing logged, nothing on /health.

F1 — the gate is now the actual guard: OCP_DIR_OVERRIDE is honored ONLY when
     NODE_ENV === "test". A production server runs without NODE_ENV and therefore CANNOT be
     redirected, however the variable reached its environment. Proven both directions:
       no NODE_ENV      + OCP_DIR_OVERRIDE=/tmp/evil-store -> /Users/<op>/.ocp/ocp.db  (ignored)
       NODE_ENV=test    + OCP_DIR_OVERRIDE=/tmp/scratch    -> /tmp/scratch/ocp.db      (honored)
     Plus: getDb() now LOGS the store whenever it is not the default. Silence was the other half
     of the bug — a server on the wrong key store looks exactly like one on the right store until
     every request 401s.

F2 — restore the 0700 guarantee on ~/.ocp. Removing keys.mjs's top-level mkdirSync (a good
     change on its own) silently dropped it: prepareSpawnHome (server.mjs:477) does
     mkdirSync(recursive) with NO mode, so on a fresh install it can create ~/.ocp as a
     world-listable 0755 parent. Verified: 755 via the spawn-home path vs 700 via resolveOcpDir.
     The invariant used to be inherited by luck; it is now stated.

F3 — test-env.mjs removes its scratch dir on exit. Otherwise the fix traded unbounded growth in
     ~/.ocp/ocp.db for unbounded growth in $TMPDIR. Verified: 2 runs, delta 0 dirs.
F4 — closeDb() clears dbPath; getDbPath() no longer hands back a path to a closed db.
F5 — dropped the dead unlinkSync import and explained the leftover HOME normalization.

New test, and it is the one that matters: "a PRODUCTION process (no NODE_ENV) must IGNORE
OCP_DIR_OVERRIDE" — so nothing can re-widen the gate without a red test.

server.mjs IS touched (one mkdirSync mode). Not endpoint-touching: no request handler, endpoint,
header, or wire field — so no cli.js citation applies (ALIGNMENT.md Rule 2 / CLAUDE.md hard-req #1).
Note memory/constitution.md § II lists keys.mjs as a protected file requiring maintainer approval.

npm test: 320 passed, 0 failed. Real ~/.ocp/ocp.db unchanged at 751 rows throughout.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VqgWJcjxrjjL9L9SkpZyXR

server.mjs

@@ -474,7 +474,12 @@ const SPAWN_HOME_DIR = `${process.env.HOME}/.ocp/spawn-home`;
 // erroring loudly — never a silent auth/credential corruption (there are no credentials here).
 function prepareSpawnHome(dir = SPAWN_HOME_DIR) {
   try {
-    mkdirSync(`${dir}/.claude`, { recursive: true });
+    // mode 0700, and it matters for the PARENT: with `recursive`, this call can create ~/.ocp
+    // itself on a fresh install (spawn homes live under it), and without an explicit mode that
+    // parent lands at the umask default — world-listable 0755. keys.mjs used to pre-create it
+    // 0700 as an import side effect; it no longer does (it resolves its dir lazily), so the
+    // 0700 guarantee has to be stated here rather than inherited by luck.
+    mkdirSync(`${dir}/.claude`, { recursive: true, mode: 0o700 });
     // Belt-and-braces: ensure no settings.json/plugins leak in (this home is fully ours).
     for (const f of [`${dir}/.claude/settings.json`, `${dir}/.claude/settings.local.json`]) {
       try { if (existsSync(f)) rmSync(f, { force: true }); } catch { /* best effort */ }