feat(newos4): the script runner runs scripts — control flow, variables, globs, redirects, stdin

MAINT-021 and MAINT-017, executed from .hermes/plans/2026-10-27_145500-newos4-script-runner.md.

- shell.js: new block parser (_parseBlocks) and executor (_runInstructions/_runSimple/_runCommand/
  _dispatchOne). `for`/`while`/`if` bodies now run, including one-line `if [ -f x ]; then y; fi`.
  Variables expand through _expandVars ($VAR, ${VAR}, $?, single quotes literal), globs expand
  through _expandGlobs (unquoted args only, per-command), and `>`/`>>` capture the command's output
  into the VFS instead of being passed to the command as text.
- shell.js: a script never answers an unknown command by calling the AI any more. It prints
  `script:<path>:<line>: <cmd>: command not found` and sets $? — the AI fallback stays for typing.
- shell.js: unclosed blocks and bad `for` headers surface as `Script <path> failed: …` (the parse
  used to sit outside the try, so a bad script crashed the runner).
- shell.js: interactive path gets the same treatment — prompt globbing and `echo hi > /f` now work.
  Cause of the asymmetry: the two code paths had separate dispatch.
- shell.js: `_isPipeAware` no longer injects the __pipebuf__ file into wc (it reads _pipeInput), and
  the module registers itself with a versioned URL and calls its own init() — registerModule() does
  not call init(), so the executeCommand wrapper was never installed from the boot bundle.
- module-fs.js: wc/head/tail/grep read piped stdin when no file operand is given; `cat` accepts
  several operands (`cat *.txt`); `ls <file>` names the file instead of printing "(empty)".
- main.html: shell.js removed from the extension list — it is already inside
  critical-ext-bundle.js, and loading it twice produced two ShellModule instances that could
  disagree about their version.

Verification:
- test-shell-script.js 27 asserts (parser, variables, globs, executor, redirect, command-not-found,
  one-line if, parse error). RED on HEAD: `TypeError: shell._parseBlocks is not a function`.
- test-shell-stdin.js 16 asserts (added by a subagent): wc -l/-c, head -n, tail -n over stdin, and
  the file-argument path unchanged.
- Suite 18/18 files; maintain --fix "node tests 18/18 pass".
- Live on v4.6.115, through the real executeCommand:
  `ls /n*.txt` -> /n1.txt · `cat /n*.txt` -> one|two · `echo hi > /r.txt` then `cat /r.txt` -> hi ·
  `cat /probe.txt | wc -l` -> 3 (bare, no __pipebuf__) ·
  `script /run.sh` -> item 1 / item 2 / item 3 / exists / command not found, exit 1, no AI routing.

1 files changed, 51 insertions, 11 deletions

diff --git a/modules/core/module-fs.js b/modules/core/module-fs.js
index 583cfda..757d1da 100644
--- a/modules/core/module-fs.js
+++ b/modules/core/module-fs.js
@@ -52,7 +52,12 @@ class FileSystemModule {
             const showLong = flags.some(f => f.includes('l'));
             const showHidden = flags.some(f => f.includes('a'));
             const files = this.terminal.fs.ls(target);
-            if (!files || files.length === 0) { this.terminal.print('(empty)', 'info'); return; }
+            if (!files || files.length === 0) {
+                // `ls somefile` used to print "(empty)": a file operand should name the file,
+                // which is also what makes `ls *.txt` (glob-expanded to several paths) readable.
+                if (target && this.terminal.fs.readFile(target) !== null) { this.terminal.print(target, 'info'); return; }
+                this.terminal.print('(empty)', 'info'); return;
+            }
             const filtered = showHidden ? files : files.filter(f => !f.name.startsWith('.'));
             if (filtered.length === 0) { this.terminal.print('(no visible files, use ls -a)', 'info'); return; }
             const maxName = Math.max(...filtered.map(f => f.name.length), 8);
@@ -92,12 +97,19 @@ class FileSystemModule {
             docs.forEach(f => this.terminal.print(`  ${f.name}  ${f.size || 0} B`, 'info'));
         };
         this.commands['cat'] = (args) => {
-            if(!args[0]) return this.terminal.print('Usage: cat <filename>', 'warning');
-            const content = this.terminal.fs.readFile(args[0]);
-            if(content !== null && content !== undefined) {
-                if (content.length === 0) this.terminal.print('(empty file)', 'info');
-                else this.terminal.print(content);
-            } else this.terminal.print('cat: ' + args[0] + ': No such file', 'error');
+            if(!args[0]) return this.terminal.print('Usage: cat <filename> [...]', 'warning');
+            // Multiple operands: `cat *.txt` is useless if only the first path is read.
+            const files = args.filter(a => !String(a).startsWith('-'));
+            let printed = 0;
+            files.forEach((f) => {
+                const content = this.terminal.fs.readFile(f);
+                if (content !== null && content !== undefined) {
+                    if (content.length === 0) this.terminal.print('(empty file)', 'info');
+                    else this.terminal.print(content);
+                    printed++;
+                } else this.terminal.print('cat: ' + f + ': No such file', 'error');
+            });
+            if (!printed && !files.length) this.terminal.print('Usage: cat <filename> [...]', 'warning');
         };
         this.commands['echo'] = (args) => {
             if (!args || args.length === 0) { this.terminal.print(''); return; }
@@ -325,7 +337,12 @@ class FileSystemModule {
                 else if (headFiles.length && /^\d+$/.test(a)) n = parseInt(a, 10);   // head f 40
                 else headFiles.push(a);
             }
-            if (!headFiles.length) return this.terminal.print('Usage: head [-n] <filename> [...] [lines]', 'warning');
+            // Piped input: `cat x | head -n 2` — no file operand means stdin, not usage.
+            const piped = this.terminal ? this.terminal._pipeInput : null;
+            if (!headFiles.length) {
+                if (piped === null || piped === undefined) return this.terminal.print('Usage: head [-n] <filename> [...] [lines]', 'warning');
+                return this.terminal.print(String(piped).split('\n').slice(0, Math.max(1, n)).join('\n'));
+            }
             const headMulti = headFiles.length > 1;
             headFiles.forEach(file => {
                 const c = this.terminal.fs.readFile(file);
@@ -354,7 +371,15 @@ class FileSystemModule {
             // v4.6.66: every path argument (packet §1). A numeric second positional is still
             // the legacy `tail <file> <count>`, not a filename.
             const tailFiles = positional.filter((p, i) => !(i > 0 && /^\d+$/.test(p)));
-            if (!tailFiles.length) return this.terminal.print('Usage: tail [-f] [-n N] <file> [...] — last N lines; -f follows changes (Ctrl+C or Esc to stop)', 'warning');
+            // Piped input: `cat x | tail -n 1` — no file operand means stdin, not usage.
+            const piped = this.terminal ? this.terminal._pipeInput : null;
+            if (!tailFiles.length) {
+                if (piped === null || piped === undefined) return this.terminal.print('Usage: tail [-f] [-n N] <file> [...] — last N lines; -f follows changes (Ctrl+C or Esc to stop)', 'warning');
+                const _in = String(piped).split('\n');
+                // same trailing-newline rule as the file path below
+                if (_in.length > 1 && _in[_in.length - 1] === '') _in.pop();
+                return this.terminal.print(_in.slice(-n).join('\n'));
+            }
             if (positional[1] && /^\d+$/.test(positional[1])) n = parseInt(positional[1], 10); // legacy back-compat
             const tailMulti = tailFiles.length > 1;
             let shownFiles = tailFiles;
@@ -524,10 +549,25 @@ class FileSystemModule {
                 else if (/^-[a-zA-Z]+$/.test(a)) { /* ignore other flags */ }
                 else files.push(a);
             });
-            if (!files.length) return this.terminal.print('Usage: wc [-l] [-w] [-c] <filename> [...]', 'warning');
+            // Piped input: `cat x | wc -l`. The pipe wrapper sets terminal._pipeInput for every
+            // stage (modules/ext/shell.js), so "no file operand" means "count stdin", not usage.
+            const piped = this.terminal ? this.terminal._pipeInput : null;
+            const stdinMode = !files.length && piped !== null && piped !== undefined;
+            if (!files.length && !stdinMode) return this.terminal.print('Usage: wc [-l] [-w] [-c] <filename> [...]', 'warning');
             const anyFlag = want.l || want.w || want.c;
             const rows = [];
             let total = { l: 0, w: 0, c: 0 };
+            if (stdinMode) {
+                const content = String(piped);
+                const r = {
+                    file: null,   // stdin has no name — GNU wc prints the bare counts
+                    l: content.split('\n').length,
+                    w: content.split(/\s+/).filter(w => w).length,
+                    c: content.length
+                };
+                total.l += r.l; total.w += r.w; total.c += r.c;
+                rows.push(r);
+            }
             files.forEach(file => {
                 const content = this.terminal.fs.readFile(file);
                 if (content === null || content === undefined) {
@@ -550,7 +590,7 @@ class FileSystemModule {
                 if (want.l || !anyFlag) out.push(r.l);
                 if (want.w || !anyFlag) out.push(r.w);
                 if (want.c || !anyFlag) out.push(r.c);
-                if (multi || (anyFlag && !(want.l && want.w && want.c))) out.push(name);
+                if ((multi || (anyFlag && !(want.l && want.w && want.c))) && name !== null) out.push(name);
                 return out.join(' ');
             };
             rows.forEach(r => this.terminal.print(fmt(r, r.file)));