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

packages/bare-os-coreutils/src/nice.js

@@ -0,0 +1,39 @@
+async function run(ctx, argv) {
+  let inc = 10
+  let i = 1
+  if (argv[i] === '-n') {
+    const n = Number.parseInt(String(argv[i + 1] ?? ''), 10)
+    if (!Number.isFinite(n) || n < 0 || n > 39) {
+      ctx.console.error('nice: invalid adjustment')
+      ctx.exitCode = 125
+      return
+    }
+    inc = n
+    i += 2
+  } else if (argv[i] && /^-\d+$/.test(argv[i])) {
+    const n = Number.parseInt(argv[i].slice(1), 10)
+    if (!Number.isFinite(n) || n < 0 || n > 39) {
+      ctx.console.error('nice: invalid adjustment')
+      ctx.exitCode = 125
+      return
+    }
+    inc = n
+    i++
+  }
+  const cmd = argv.slice(i)
+  if (!cmd.length) {
+    ctx.console.error('usage: nice [-n increment] utility [argument...]')
+    ctx.exitCode = 125
+    return
+  }
+  if (typeof ctx.runBinCommand !== 'function') {
+    ctx.console.error('nice: runBinCommand is not available')
+    ctx.exitCode = 125
+    return
+  }
+  const env = ctx.vfs?.env
+  if (env && typeof env === 'object') {
+    env.BARE_OS_SIMULATED_NICE = String(inc)
+  }
+  await ctx.runBinCommand(cmd)
+}