feat(client): typo-safe protocol enums + context manager; add wafer_tool example

Interface cleanup so the report_* family matches the typo-safe ethos of
eq.names instead of leaking raw protobuf errors on a misspelled value.

- Milestone / ModuleState / JobState: importable str-enums (member == its
  wire name, so plain strings still work) — autocomplete + a typo-checked
  happy path. The clean rule: equipment-specific *names* live on eq.names;
  fixed protocol *value-sets* are enums.
- _enum_value(): resolves an enum-or-string arg client-side and, on a bad
  value, raises ValueError with a close-match hint *before* the wire. Wired
  into report_job / report_substrate / report_module / request_control_state
  (all previously raised a raw protobuf ValueError).
- Equipment is now a context manager (with Equipment(...) as eq: ...).
- examples/wafer_tool.py: a cluster tool tracking one wafer through one
  module end-to-end (E90 + E157), showing the enums + context manager.
- tests/test_enums.py: asserts the enums stay in lockstep with the proto and
  that the typo path is helpful. Wired into run_interop.sh (pyclient step).
- Interop drives both the enum and string forms on the wire + the ValueError
  typo path. Docs (ch16/ch42) updated; names-vs-enums rule documented.

All Python unit tests + 25 pyclient interop checks pass.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tools/run_interop.sh

@@ -98,6 +98,8 @@ note "pyclient: secsgem_client package + secsgem-py host vs secs_gemd"
   set -e
   compose run --rm --no-deps -e PYTHONPATH=/app/clients/python interop \
     python3 /app/clients/python/tests/test_values.py
+  compose run --rm --no-deps -e PYTHONPATH=/app/clients/python interop \
+    python3 /app/clients/python/tests/test_enums.py
   compose up -d --no-deps gemd
   sleep 2
   compose run --rm --no-deps -e PYTHONPATH=/app/clients/python interop \