chore: clean up clear-cut ESLint warnings (#732) (#734)

Pay down pre-existing error→warn lint debt. Removes dead imports/vars, unused functions, redundant regex/string escapes, and stale eslint-disable directives; converts unused `catch (_e)` to optional catch binding (src/*.cts).

No behavior change. Lint 345→125 warnings (0 errors); deferred categories (n/no-process-exit, test-sleeps, control-regex) tracked in #732 for follow-up. Full test suite green (0 failures); code-review verified all removals unused and all escape fixes semantics-preserving.

Closes #732

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

src/command-routing-hub.cts

@@ -271,7 +271,7 @@ function createHub({ cjsRegistry, manifest, logger }: HubOptions = {}): { dispat
     }
     // err variant: already has kind + typed payload
     // Double-cast through unknown to satisfy strict index-signature check.
-    return hubResult as unknown as Record<string, unknown>; // eslint-disable-line @typescript-eslint/no-unsafe-return
+    return hubResult as unknown as Record<string, unknown>;
   }
 
   /**