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, 10 insertions, 1 deletions

diff --git a/modules/core/module-fs.js b/modules/core/module-fs.js
index fd1dfc1..415bd92 100644
--- a/modules/core/module-fs.js
+++ b/modules/core/module-fs.js
@@ -238,7 +238,16 @@ 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);