feat(newos4): register `test` / `[` so chains decide locally instead of asking a model (v4.6.135)

`[ -f "/qt.txt" ] && echo exists` — the probe that closed the v4.6.132 batch — was not a shell test
at all: both commands were unregistered, so the line fell through to the AI fallback and a model was
asked whether a file exists. `_evalTest()` has implemented `-f -d -e -z -n ! = !=` for the if/while
parser since the script runner was written; only the command was missing.

  * `test` and `[` registered in ShellModule. Success resolves silently; false rejects with a
    `silent` error so `&&`/`||` skip it — POSIX prints nothing on exit 1.
  * `[` requires the closing bracket (`[ : missing ']'`), and that message is NOT silent.
  * `test` already names the on-demand regression-suite runner ("test auto" / "test list" in
    help.html). A argv that does not look like a test expression (`-f`/`-d`/`-e`/`-z`/`-n`/`!`,
    or `a = b` / `a != b`) is delegated to the handler registered before us, so `test auto`
    still runs the suite and the two meanings cannot collide.
  * terminal.dispatchCommand() now honours `err.silent` — without it a top-level `test -f /nope`
    printed `Error in ShellModule.test:` (measured on v4.6.134, fixed in v4.6.135).
  * help.html documents the bracket form next to the existing `test` row.

Three tags were minted minutes apart — v4.6.133 (commands), v4.6.134 (suite delegation),
v4.6.135 (silent top-level) — each a real cache-bust for a fix that superseded the previous build;
the net change is this commit.

Verification
  node modules/test/test-shell-test-cmd.js -> 24/24 pass (RED against HEAD: "test command
      registered" fails, "m.commands.test is not a function")
  node modules/test/test-pipe-guard.js     -> all seven flags true
  node modules/test/test-parse-args.js     -> 28/28 · daily job -> node tests 22/22 pass
  newos4-maintain.py -> atlas 355 commands (was 354), modules-index 349, help 364/364
  live v4.6.135, read from the terminal DOM:
    [ -f /qt.txt ] && echo F135          -> F135
    test -f /nope || echo M135           -> M135
    [ -d /nope ] && echo BAD || echo N134-> N134   (false branch skipped, nothing printed)
    test                                 -> no output (suite not loaded; POSIX false)
    test -f /nope                        -> no output
    js "a b".length | wc -c              -> 1       (v4.6.132 pipe fix still intact)
  The AI fallback is no longer reachable for a bracketed file test.

1 files changed, 42 insertions, 2 deletions

diff --git a/modules/ext/critical-ext-bundle.js b/modules/ext/critical-ext-bundle.js
index 0f2e1b9..53f1205 100644
--- a/modules/ext/critical-ext-bundle.js
+++ b/modules/ext/critical-ext-bundle.js
@@ -170,6 +170,46 @@ class ShellModule {
         this.commands['script'] = (args) => this._cmdScript(args);
         this.commands['sh'] = (args) => this._cmdScript(args);
         this.commands['set'] = () => this._cmdSet();
+        // v4.6.133: `test` / `[` were not registered, so `[ -f /x ] && echo yes` fell through to the
+        // AI fallback and asked a model whether a file exists. _evalTest() already implemented the
+        // operators (-f -d -e -z -n ! = !=) for the if/while parser; the command was simply missing.
+        // `test` already means "run the regression suite" in the on-demand test-suite module, so a
+        // non-expression argument list is delegated to whatever handler was registered before us.
+        const prevTest = this.commands['test'];
+        this.commands['test'] = (args) => this._cmdTest(args, 'test', prevTest);
+        this.commands['['] = (args) => this._cmdTest(args, '[');
+    }
+
+    /** True when the argv looks like a POSIX test expression rather than a suite-runner subcommand. */
+    _looksLikeTest(expr) {
+        if (!expr) return false;
+        if (/^(?:!(?:\s|$)|-[fderwxszn]\b)/.test(expr)) return true;      // `-f x`, `! -d y`
+        if (/\s(?:=|==|!=)\s/.test(expr)) return true;                    // `a = b`
+        return false;
+    }
+
+    /** POSIX-ish `test`/`[`: silent on success, throws a silent error on false so `&&`/`||` skip. */
+    _cmdTest(args, name, fallback) {
+        let expr = (args || []).join(' ').trim();
+        if (name === 'test' && !this._looksLikeTest(expr) && typeof fallback === 'function') {
+            return fallback(args);          // `test`, `test auto`, `test list` -> the suite runner
+        }
+        if (name === '[') {
+            if (!expr.endsWith(']')) throw new Error("[ : missing ']'");
+            expr = expr.slice(0, -1).trim();
+        }
+        if (!expr) {                       // `test` with no expression: false, and no output
+            const e = new Error(''); e.silent = true; throw e;
+        }
+        if (!this._evalTest(expr)) {
+            const e = new Error(''); e.silent = true; throw e;   // POSIX: exit 1 prints nothing
+        }
+    }
+
+    /** Error printer shared by the shell paths: `silent` errors are control flow (a false test), not failures. */
+    _printErr(term, e) {
+        if (!e || e.silent) return;
+        (term || this.terminal).print('Error: ' + (e.message || e), 'error');
     }
 
     // ── Hook into terminal.executeCommand ──
@@ -259,7 +299,7 @@ class ShellModule {
                                     await self.commands[cmd](args);
                                     lastOk = true;
                                 } catch(e) {
-                                    this.print('Error: ' + e.message, 'error');
+                                    self._printErr(this, e);
                                     lastOk = false;
                                 }
                             } else {
@@ -267,7 +307,7 @@ class ShellModule {
                                     await this.security.checkAndRun(expandedCmd);
                                     lastOk = true;
                                 } catch(e) {
-                                    this.print('Error: ' + e.message, 'error');
+                                    self._printErr(this, e);
                                     lastOk = false;
                                 }
                             }