sh: add POSIX-like -c support and complete shell subset gaps

Implement sh -c COMMAND [NAME [ARG...]] in /bin/sh, add shell function
declarations/invocation support, expand export semantics (NAME, NAME=value, -p),
and make until/loop-control behavior available by default. Add focused shell
tests and update sh man-page option docs.

kernel/bin/sh

@@ -88,9 +88,9 @@ function bareOsEmitRaw(ctx, chunk) {
 }
 
 async function run(ctx, argv) {
-  const script = argv[1]
-  if (script == null) {
-    ctx.console.error('usage: sh SCRIPT')
+  const mode = argv[1]
+  if (mode == null) {
+    ctx.console.error('usage: sh -c COMMAND [NAME [ARG ...]] | sh SCRIPT')
     ctx.exitCode = 2
     return
   }
@@ -99,6 +99,39 @@ async function run(ctx, argv) {
     ctx.exitCode = 1
     return
   }
+  if (mode === '-c') {
+    const command = argv[2]
+    if (command == null) {
+      ctx.console.error('sh: option requires an argument -- c')
+      ctx.console.error('usage: sh -c COMMAND [NAME [ARG ...]] | sh SCRIPT')
+      ctx.exitCode = 2
+      return
+    }
+    const env = ctx.vfs?.env
+    /** @type {Record<string, string | undefined> | null} */
+    const saved = env && typeof env === 'object' ? {} : null
+    if (saved && env) {
+      for (const k of ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '#']) {
+        saved[k] = env[k]
+      }
+      env['0'] = argv[3] ?? 'sh'
+      const args = argv.slice(4)
+      for (let i = 1; i <= 9; i++) env[String(i)] = args[i - 1] ?? ''
+      env['#'] = String(args.length)
+    }
+    try {
+      await ctx.execLine(command)
+    } finally {
+      if (saved && env) {
+        for (const [k, v] of Object.entries(saved)) {
+          if (v == null) delete env[k]
+          else env[k] = v
+        }
+      }
+    }
+    return
+  }
+  const script = mode
   let buf
   try {
     buf = await ctx.vfs.readFile(script)

kernel/etc/bare-os/posix_utilities.json

@@ -1,7 +1,7 @@
 {
   "schema": 2,
   "profileId": "bare-os-posix-like",
-  "generatedAt": "2026-04-26T19:04:18.264Z",
+  "generatedAt": "2026-04-26T19:19:08.534Z",
   "note": "Sparse POSIX Issue 7 coverage hints for /bin utilities. Omitted command names are not yet profiled here.",
   "commandIndex": [
     {

kernel/lib/bare/shell-completion.json

@@ -1,6 +1,6 @@
 {
   "schema": 1,
-  "atMs": 1777230258263,
+  "atMs": 1777231148534,
   "commands": [
     "agent",
     "appctl",

kernel/share/man/man.json

@@ -1,6 +1,6 @@
 {
   "schemaVersion": 1,
-  "generatedAt": "2026-04-26T19:04:18.469Z",
+  "generatedAt": "2026-04-26T19:19:08.715Z",
   "pages": [
     {
       "name": "agent",
@@ -3211,8 +3211,13 @@
       "synopsis": [
         "sh [OPTION]... [OPERAND]..."
       ],
-      "description": "Runs a shell script file line-by-line via ctx.execLine (same language as the interactive booter shell). This is not the interactive REPL; see man bare-os-shell for session builtins, pipelines, and jobs.",
-      "options": [],
+      "description": "Runs shell commands via ctx.execLine (same language as the interactive booter shell). Supports command-string mode (`-c`) and script-file mode (`sh SCRIPT`). This is not the interactive REPL; see man bare-os-shell for session builtins, pipelines, and jobs.",
+      "options": [
+        {
+          "flag": "-c COMMAND [NAME [ARG ...]]",
+          "meaning": "Execute command string and set positional parameters for that command context."
+        }
+      ],
       "keywords": [
         "sh",
         "bare-os",