feat(booter): complete P2P POSIX roadmap items and doc alignment

- ADRs under docs/adr/; KERNEL_CONTRACT + env appendix + handbook updates
- socketMsgSurface schema 5; replication_snapshot schema 2; syscall/example + tests
- MBR pacing docs/microbench; export mbrReadTimeoutMsForDisk; shell passthrough envs
- verify-ctx-api-feature-bits: syscall schema vs posix-compliance-matrix
- Wasm hostname import, disk.os snapshot hints, kernel-ext resolution docs
- coreutils nice + matrix/dashboard; syscalls.example ctxApiVersion 1.51.1
- Seeder kernel rsync parity; assorted booter/protocol doc fixes

docs/schemas/bare-os-syscalls.schema.json

@@ -57,7 +57,7 @@
     },
     "socketMsgSurface": {
       "type": "object",
-      "description": "sendmsg/recvmsg metadata (defaults ENOTSUP; bridge uses recv/recvfrom buffers only); schema 3 adds ancillaryControl rejection contract",
+      "description": "sendmsg/recvmsg metadata (defaults ENOTSUP; bridge uses recv/recvfrom buffers only); schema 5 documents SOCK_STREAM logical SCM_RIGHTS parity with SOCK_DGRAM",
       "properties": {
         "schema": { "type": "integer" },
         "ancillaryControl": {