Rename config templates: .templ → -sim.json.tpl, config_real.json → -real.json.tpl

Consistent naming: config-sim.json.tpl and config-real.json.tpl.
Update README and TODO references accordingly.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SH2D4LRuCnhLSzoYerAfJX

components/pid/TODO.md

@@ -58,7 +58,7 @@ git history for `temp_controller.py`/`temp_controller_smith.py`).
   schema/dataclass validation layer at config-load would surface
   errors immediately instead of mid-`__init__` — and would have caught
   the dead `TempCtrl.Kalman` / `Model.kn` / `Plant.kn` keys that used
-  to sit unused in `config.json.templ`/`.sim` (since deleted), and the
+  to sit unused in `config-sim.json.tpl`/`.sim` (since deleted), and the
   `Model.gain`/`Plant.gain` keys that did the same in `config.json.sim`
   before that file was removed entirely — `Pot` dropped `gain`
   entirely, see `components/plant/TODO.md`.