chore(#2453): resolve the uniform-router-param conflict and clear the warning floor (#2489)

npx eslint . reported 0 errors, 53 warnings. The floor eroded the signal: a
genuinely new warning had to be spotted against noise, so 'lint is clean' was not
usable as a check. This takes it to zero.

Fifty of the 53 were one category in gsd-core/bin/gsd-tools.cjs — all unused
ARGUMENTS (error x30, cwd x10, raw x7, args x3), never unused variables. They are
the Command Routing Hub's uniform handler signature, function routeX({ args, cwd,
raw, error }), declared identically whether or not a handler uses all four
members. argsIgnorePattern: '^_' is structurally in conflict with that convention:
satisfying it would mean _-prefixing ~50 parameters and making the signature
non-uniform across the table. Option 1 of #2453: disable args checking for that
file only, keeping varsIgnorePattern intact so genuinely dead variables (the #2379
class) still surface — verified by injecting an unused variable, which still warns.

This is the config decision #732 explicitly deferred ('Severities stay warn (no
config change in this pass)').

The remaining three predate the issue's count of 51 and are real defects, not
suppressions:

- tests/workflow-compat.test.cjs — the step-9 lookahead used (?=\*\*10\.|\z).
  \z is a Perl/Ruby end-of-input anchor with NO meaning in JavaScript; it matched
  a literal 'z', so the lazy span silently stopped at the first z whenever **10.
  was absent, truncating the captured step and letting the assertion pass against
  a partial block. Corrected to $.
- tests/debugger-prevention.test.cjs — an unused RegExp built one line above the
  one actually used. Removed.
- tests/installer-migrations.test.cjs — try/finally inside a test body, which
  CONTRIBUTING prohibits ('verbose, masks test failures, not an approved
  pattern'); the unused t was the symptom. Converted to t.after().

Closes #2453

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

tests/installer-migrations.test.cjs

@@ -2654,36 +2654,34 @@ describe('migration.plan()', () => {
 
   test('a regular managed file is still backed up by content (no behavior change)', (t) => {
     const configDir = createTempInstall();
-    try {
-      writeFile(configDir, 'extensions/gsd.cjs', 'locally patched extension\n');
-      writeManifest(configDir, { 'extensions/gsd.cjs': sha256('the original extension\n') });
+    t.after(() => cleanup(configDir));
 
-      const result = runInstallerMigrations({
-        configDir,
-        runtime: 'pi',
-        scope: 'global',
-        migrations: [piExtensionMigration],
-        now: () => '2026-07-20T00:00:00.000Z',
-      });
+    writeFile(configDir, 'extensions/gsd.cjs', 'locally patched extension\n');
+    writeManifest(configDir, { 'extensions/gsd.cjs': sha256('the original extension\n') });
 
-      const backupAction = result.plan.actions.find((a) => a.type === 'backup-and-remove');
-      assert.ok(backupAction, 'expected backup-and-remove for the locally patched file');
+    const result = runInstallerMigrations({
+      configDir,
+      runtime: 'pi',
+      scope: 'global',
+      migrations: [piExtensionMigration],
+      now: () => '2026-07-20T00:00:00.000Z',
+    });
 
-      // The PLAN carries backupRelPath: null — the concrete backup location is
-      // chosen during apply and recorded in the journal, so read it from there.
-      const journal = JSON.parse(fs.readFileSync(path.join(configDir, result.journalRelPath), 'utf8'));
-      const journalled = journal.actions.find((a) => a.backupRelPath);
-      assert.ok(journalled, 'apply must record the backup path in the journal for the user');
-      const backupPath = path.join(configDir, journalled.backupRelPath);
-      assert.equal(
-        fs.readFileSync(backupPath, 'utf8'),
-        'locally patched extension\n',
-        'a real file must still be backed up by content so the user can recover it',
-      );
-      assert.ok(!fs.existsSync(path.join(configDir, 'extensions', 'gsd.cjs')));
-    } finally {
-      cleanup(configDir);
-    }
+    const backupAction = result.plan.actions.find((a) => a.type === 'backup-and-remove');
+    assert.ok(backupAction, 'expected backup-and-remove for the locally patched file');
+
+    // The PLAN carries backupRelPath: null — the concrete backup location is
+    // chosen during apply and recorded in the journal, so read it from there.
+    const journal = JSON.parse(fs.readFileSync(path.join(configDir, result.journalRelPath), 'utf8'));
+    const journalled = journal.actions.find((a) => a.backupRelPath);
+    assert.ok(journalled, 'apply must record the backup path in the journal for the user');
+    const backupPath = path.join(configDir, journalled.backupRelPath);
+    assert.equal(
+      fs.readFileSync(backupPath, 'utf8'),
+      'locally patched extension\n',
+      'a real file must still be backed up by content so the user can recover it',
+    );
+    assert.ok(!fs.existsSync(path.join(configDir, 'extensions', 'gsd.cjs')));
   });
 
   // In-flight failure recovery: when a later step of the SAME apply() attempt