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

kernel/etc/bare-os/posix_utilities.json

@@ -1,7 +1,7 @@
 {
   "schema": 2,
   "profileId": "bare-os-posix-like",
-  "generatedAt": "2026-04-05T18:43:53.989Z",
+  "generatedAt": "2026-04-05T19:03:41.000Z",
   "note": "Sparse POSIX Issue 7 coverage hints for /bin utilities. Omitted command names are not yet profiled here.",
   "commandIndex": [
     {
@@ -316,6 +316,10 @@
       "name": "nano",
       "tier": "tier1_bin"
     },
+    {
+      "name": "nice",
+      "tier": "tier1_bin"
+    },
     {
       "name": "nl",
       "tier": "tier1_bin"

kernel/etc/bare-os/syscalls.example.json

@@ -1,6 +1,6 @@
 {
   "schemaVersion": 10,
-  "ctxApiVersion": "1.51.0",
+  "ctxApiVersion": "1.51.1",
   "posixProfile": {
     "id": "bare-os-posix-like",
     "version": "1.0.15"