feat: POSIX/P2P roadmap — multisig shape, socket bridge, bin index, docs

- Unify pear.multisig.json validation via bare-os-protocol + kernel boot fragment
- Socket bridge: SCM_RIGHTS path, ancillary handling, TCP half-close/shutdown how,
  connect tcpRecvQueue + poll/recv EOF and EPIPE-shaped errors
- Bin manifest / Hyperbee hints schema 2 + namesDigest; batch-write invalidation
- Host booter structured logging; BOOT_PERF_DETAIL bare_stdlib_merge_ns timing
- Wasm kernel optional syscall imports; security_posture rotation hints schema 2
- Shell errexit inside compound bodies; expand getconf/_SC_* and bareOsGetconfSysconf
- Subprocess bridge snapshot timeoutPolicy; blind-relay protomux backpressure tests
- Pear updater minimal delegate example + verify-pear scan; holepunch drift repos
- Refresh handbook, kernel-image, syscall-socket-contract, posix matrix, PEAR-RUN

Rebuild coreutils/bundles; bundle kernel; keep seeder/kernel parity.

kernel/lib/init/init-main.js

@@ -2486,14 +2486,7 @@ async function runKernelExtDropins(ctx, opts = {}) {
         }
       } else {
         const mj = JSON.parse(ctx.b4a.toString(mbuf))
-        const signers = mj && mj.signers
-        const quorum = mj && mj.quorum
-        const badShape =
-          !Array.isArray(signers) ||
-          typeof quorum !== 'number' ||
-          quorum < 1 ||
-          quorum > signers.length
-        if (badShape) {
+        if (!bareOsPearMultisigShapeOk(mj)) {
           bootStructuredLog(
             ctx,
             'error',