fix(newos4): an invalid grep pattern returns a message, not an exception (v4.6.64)

Packet 8. `new RegExp(pattern)` sat unguarded in the terminal grep handler and in
VFS find()/grep(), so a bad pattern threw out of the command handler into the error
ledger -- the same ledger packet 2 had to stop trusting.

- module-fs.js grep: compile in try/catch, print
  "grep: invalid pattern: <pattern> (<engine message>)" as a warning and return
- virtual-fs.js find()/grep(): same guard, return [] and stash the message on
  _lastPatternError instead of throwing into the module error wrapper

Verified live on v4.6.64 with the packet's own repro: `grep "/\bug_id\" file` prints
the message, the error counter stays 0 (was: one ledger entry per call), a valid
pattern still matches, and fs.grep('[') returns [] instead of throwing.

1 files changed, 18 insertions, 3 deletions

diff --git a/modules/core/core-bundle.js b/modules/core/core-bundle.js
index df4563d..a5e9a79 100644
--- a/modules/core/core-bundle.js
+++ b/modules/core/core-bundle.js
@@ -824,7 +824,10 @@ class VirtualFileSystem {
             dir = resolved.dir;
         }
         const results = [];
-        const regex = new RegExp(pattern, 'i');
+        // v4.6.64: an invalid pattern must not throw into the error ledger (packet §8).
+        let regex;
+        try { regex = new RegExp(pattern, 'i'); }
+        catch (e) { this._lastPatternError = e.message; return []; }
         for (const name of Object.keys(dir.content)) {
             const fullPath = path ? path + '/' + name : name;
             if (regex.test(name)) {
@@ -838,7 +841,10 @@ class VirtualFileSystem {
     }
     grep(pattern, path = '') {
         const results = [];
-        const regex = new RegExp(pattern, 'i');
+        // v4.6.64: see find() above — a bad pattern is a result, not an exception.
+        let regex;
+        try { regex = new RegExp(pattern, 'i'); }
+        catch (e) { this._lastPatternError = e.message; return []; }
         const files = this.find('.', path).filter(e => e.type === 'file');
         for (const file of files) {
             const content = this.readFile(file.path);
@@ -6636,7 +6642,16 @@ class FileSystemModule {
             }
             const pattern = args[ai]; const target = args[ai + 1];
             if (!pattern) return this.terminal.print('Usage: grep [-n] [-i] [-c] [-l] <pattern> [filename]', 'warning');
-            const re = new RegExp(pattern, opt.ignoreCase ? 'i' : '');
+            // 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).
+            let re;
+            try {
+                re = new RegExp(pattern, opt.ignoreCase ? 'i' : '');
+            } catch (e) {
+                this.terminal.print('grep: invalid pattern: ' + pattern + ' (' + e.message + ')', 'warning');
+                return;
+            }
             const hits = (line) => (opt.invert ? !re.test(line) : re.test(line));
             if (target) {
                 const c = this.terminal.fs.readFile(target);