refactor: fix unused imports, long lines, and type issues

Remove 35+ unused imports across 20+ files (W0611). Wrap 19 lines
to fit under 100 character limit (C0301). Add type casts and
annotations in egress_addon_core.py to resolve pyright errors
caused by JSON parsing of untyped objects.

Key changes:
- Remove unused imports (abstractmethod, mock utilities, etc)
- Split long lines at logical breaks (method calls, error messages)
- Add typing.cast() for proper type inference in JSON parsing
- Explicit type annotations for dict/list accesses

Results:
- Pylint rating: 8.73/10
- egress_addon_core.py: 0 pyright errors (was 15)
- All W0611 and C0301 issues fixed

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

tests/unit/test_plan_print_parity.py

@@ -220,7 +220,11 @@ class TestEgressPrintParity(unittest.TestCase):
                 indent_prefix = ln[:idx]
                 result.append(ln)
             elif collecting:
-                if ln.startswith(indent_prefix) and "egress" not in ln and ":" not in ln.lstrip()[:20]:
+                if (
+                    ln.startswith(indent_prefix)
+                    and "egress" not in ln
+                    and ":" not in ln.lstrip()[:20]
+                ):
                     result.append(ln)
                 else:
                     break