fix(newos4): grep, head and tail take every path argument (v4.6.67)

Packet 1's multi-path ask was only honoured by wc in v4.6.58 — grep read only
args[ai+1] and head/tail only positional[0], so `grep x a b` searched `a`, printed
one file's hits, and exited 0. Same silent drop, three more commands.

- grep: loops every path; multiple files print `file:line: text`, `-c` prints one
  count per file, missing files are reported per file and excluded from the summary
  count; single-file output unchanged
- head: every path, `==> file <==` header when more than one; `head f 40` still works
- tail: every path with headers; a numeric second positional is still the legacy
  `tail <file> <count>`; `-f` warns and follows only the first file instead of
  printing all of them and claiming otherwise

Verified live on v4.6.67:
grep "bug_id" a b        -> a:2 + b:3 + "2 match(es) in 2 file(s)"
grep -c "alpha" a b      -> one count per file
grep "alpha" a missing   -> hits from a, per-file error, "in 1 file(s)"
head -n 1 a b            -> header + first line for each
tail -n 1 a b            -> header + last line for each
tail a 2                 -> legacy count still honoured
tail -f a b              -> warns, follows a only

1 files changed, 71 insertions, 32 deletions

diff --git a/modules/core/core-bundle.js b/modules/core/core-bundle.js
index a5e9a79..e4cd832 100644
--- a/modules/core/core-bundle.js
+++ b/modules/core/core-bundle.js
@@ -6641,7 +6641,7 @@ class FileSystemModule {
                 ai++;
             }
             const pattern = args[ai]; const target = args[ai + 1];
-            if (!pattern) return this.terminal.print('Usage: grep [-n] [-i] [-c] [-l] <pattern> [filename]', 'warning');
+            if (!pattern) return this.terminal.print('Usage: grep [-n] [-i] [-c] [-l] <pattern> [filename ...]', 'warning');
             // v4.6.64: an invalid pattern is user input, not a system fault. It used to throw
             // out of the command handler into the error ledger, polluting the counter that
             // packet §2 says nobody can trust (packet §8).
@@ -6653,20 +6653,36 @@ class FileSystemModule {
                 return;
             }
             const hits = (line) => (opt.invert ? !re.test(line) : re.test(line));
-            if (target) {
-                const c = this.terminal.fs.readFile(target);
-                if (c === null || c === undefined) return this.terminal.print('grep: ' + target + ': No such file', 'error');
-                const lines = c.split('\n');
-                let count = 0;
-                lines.forEach((line, i) => {
-                    if (!hits(line)) return;
-                    count++;
-                    if (!opt.count && !opt.files) this.terminal.print((i + 1) + ': ' + line);
+            // v4.6.66: every path argument is searched. `grep x a b` used to read only `a` and
+            // exit clean — a silent false negative (packet §1).
+            const grepFiles = args.slice(ai + 1).filter(Boolean);
+            if (grepFiles.length) {
+                const multi = grepFiles.length > 1;
+                let grand = 0;
+                let readFiles = 0;
+                grepFiles.forEach(file => {
+                    const c = this.terminal.fs.readFile(file);
+                    if (c === null || c === undefined) {
+                        this.terminal.print('grep: ' + file + ': No such file', 'error');
+                        return;
+                    }
+                    readFiles++;
+                    let count = 0;
+                    c.split('\n').forEach((line, i) => {
+                        if (!hits(line)) return;
+                        count++;
+                        if (opt.count || opt.files) return;
+                        this.terminal.print(multi ? (file + ':' + (i + 1) + ': ' + line) : ((i + 1) + ': ' + line));
+                    });
+                    grand += count;
+                    if (opt.files) { if (count) this.terminal.print(file); }
+                    else if (opt.count) this.terminal.print(multi ? (file + ':' + count) : String(count));
+                    else if (!count && !multi) this.terminal.print('(no matches)', 'info');
                 });
-                if (opt.files && count) this.terminal.print(target);
-                if (count === 0) this.terminal.print('(no matches)', 'info');
-                else if (opt.count) this.terminal.print(String(count));
-                else if (!opt.files) this.terminal.print(count + ' match(es)', 'text-muted');
+                if (!opt.count && !opt.files) {
+                    if (grand === 0) this.terminal.print('(no matches)', 'info');
+                    else this.terminal.print(grand + ' match(es)' + (multi ? ' in ' + readFiles + ' file(s)' : ''), 'text-muted');
+                }
             } else {
                 const dir = this.terminal.fs.getCurrentDir();
                 if (!dir) return this.terminal.print('grep: cannot search', 'error');
@@ -6689,18 +6705,25 @@ class FileSystemModule {
         };
         this.commands['head'] = (args) => {
             // 2026-10-21: accept `head -40 f`, `head -n 40 f` and `head f 40`.
-            let n = 10, file = null;
+            // v4.6.66: every path argument, not just the first (packet §1).
+            let n = 10;
+            const headFiles = [];
             for (let i = 0; i < (args || []).length; i++) {
                 const a = args[i];
                 if (/^-\d+$/.test(a)) n = parseInt(a.slice(1), 10);
-                else if (a === '-n') { const v = parseInt(args[i + 1], 10); if (!isNaN(v)) n = v; i++; }
+                else if (a === '-n') { const v = parseInt(args[i + 1], 10); if (!isNaN(v)) { n = v; i++; } }
                 else if (/^-[a-zA-Z]+$/.test(a)) { /* ignore other flags */ }
-                else if (!file) file = a;
-            }
-            if (!file) return this.terminal.print('Usage: head [-n] <filename> [lines]', 'warning');
-            const c = this.terminal.fs.readFile(file);
-            if (c === null || c === undefined) return this.terminal.print('head: ' + file + ': No such file', 'error');
-            this.terminal.print(c.split('\n').slice(0, Math.max(1, n)).join('\n'));
+                else if (headFiles.length && /^\d+$/.test(a)) n = parseInt(a, 10);   // head f 40
+                else headFiles.push(a);
+            }
+            if (!headFiles.length) return this.terminal.print('Usage: head [-n] <filename> [...] [lines]', 'warning');
+            const headMulti = headFiles.length > 1;
+            headFiles.forEach(file => {
+                const c = this.terminal.fs.readFile(file);
+                if (c === null || c === undefined) return this.terminal.print('head: ' + file + ': No such file', 'error');
+                if (headMulti) this.terminal.print('==> ' + file + ' <==', 'text-muted');
+                this.terminal.print(c.split('\n').slice(0, Math.max(1, n)).join('\n'));
+            });
         };
         this.commands['tail'] = (args) => {
             const self = this;
@@ -6719,17 +6742,33 @@ class FileSystemModule {
                 else if (a.startsWith('-')) return this.terminal.print('tail: invalid option: ' + a, 'error');
                 else positional.push(a);
             }
-            const file = positional[0];
-            if (!file) return this.terminal.print('Usage: tail [-f] [-n N] <file> — last N lines; -f follows changes (Ctrl+C or Esc to stop)', 'warning');
-            if (positional[1] && /^\d+$/.test(positional[1])) n = parseInt(positional[1], 10); // legacy back-compat: tail <file> <count>
-            const c = this.terminal.fs.readFile(file);
-            if (c === null || c === undefined) return this.terminal.print('tail: ' + file + ': No such file', 'error');
-            // 2026-10-21: a trailing newline produced an empty last element, so `tail -n 1`
-            // printed a blank line instead of the final line.
-            const _all = c.split('\n');
-            if (_all.length > 1 && _all[_all.length - 1] === '') _all.pop();
-            this.terminal.print(_all.slice(-n).join('\n'));
+            // 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+$/.test(p)));
+            if (!tailFiles.length) return this.terminal.print('Usage: tail [-f] [-n N] <file> [...] — last N lines; -f follows changes (Ctrl+C or Esc to stop)', 'warning');
+            if (positional[1] && /^\d+$/.test(positional[1])) n = parseInt(positional[1], 10); // legacy back-compat
+            const tailMulti = tailFiles.length > 1;
+            let shownFiles = tailFiles;
+            if (follow && tailMulti) {
+                this.terminal.print('tail: -f needs a single file — following ' + tailFiles[0] + ' only', 'warning');
+                shownFiles = [tailFiles[0]];
+            }
+            let firstContent = null;
+            shownFiles.forEach(f2 => {
+                const cc = this.terminal.fs.readFile(f2);
+                if (cc === null || cc === undefined) return this.terminal.print('tail: ' + f2 + ': No such file', 'error');
+                if (shownFiles.length > 1) this.terminal.print('==> ' + f2 + ' <==', 'text-muted');
+                // 2026-10-21: a trailing newline produced an empty last element, so `tail -n 1`
+                // printed a blank line instead of the final line.
+                const _all = cc.split('\n');
+                if (_all.length > 1 && _all[_all.length - 1] === '') _all.pop();
+                this.terminal.print(_all.slice(-n).join('\n'));
+                if (firstContent === null) firstContent = cc;
+            });
+            const file = tailFiles[0];
+            const c = firstContent === null ? '' : firstContent;
             if (!follow) return;
+            if (c === '') return;   // v4.6.66: the only file was unreadable — nothing to follow
             // AI tool calls cannot press Ctrl+C — auto-downgrade to a bounded read instead of a live timer
             if (this.terminal.security && this.terminal.security._aiToolDepth > 0) {
                 return this.terminal.print('tail: follow mode (-f) is interactive-only; showing last lines instead (use tail -n ' + Math.max(n, 50) + ' for more)', 'warning');