feat(spells): allow spells to ignore spell resistance

SpellSpec gains spell_resistance: bool = True (JSON 'spell_resistance'). When false, _spell_delivery_blocked skips the targeted SR check and _apply_area_effect skips the per-creature SR check (threaded through the effect chain). Verified each imported spell against the local KB and set false on the 28 whose SRD block says 'Spell Resistance: no' (Acid Arrow, Flurry of Snowballs, Web, Darkness, Sanctuary, the Protection from X spells, etc.). Added no-SR targeted/area tests and a high-SR control in test_spell_resistance.py, and the README.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

data/spells/unseen_servant.json

@@ -6,6 +6,7 @@
   "save": "none",
   "base_dc": 10,
   "cast_time": "standard",
+  "spell_resistance": false,
   "effects": [],
   "description": "An invisible, mindless, shapeless force performs simple tasks at your command for 1 hour/level: fetching, opening unstuck doors, holding chairs, cleaning or mending (effective Strength 2, speed 15 ft., no attacks, DC 10 skill limit). No combat effect: object manipulation by invisible servants is not modeled by the engine."
 }