feat(llm-pi-ai): per-model reasoningEfforts and reasoning-dispatch compat switches

A model entry's reasoningEfforts dict declares its selectable thinking
levels — key = offered level, value = the wire spelling dispatch sends;
only off may leave the value empty (supported, send nothing). false
strips reasoning from a catalog model; every level is materialized
explicitly into pi-ai's thinkingLevelMap so nobody has to know pi-ai's
asymmetric absent-key defaulting. compat.thinkingFormat and
compat.supportsReasoningEffort become configurable on the route and per
model (model > route > catalog entry > pi-ai's URL-derived guess),
openai-completions only, so a private gateway speaking the DeepSeek
reasoning dialect no longer depends on its URL being recognizable.
Record-typed drift gates pin both enums to pi-ai's, and an unserviceable
declaration is refused at the write that produced it, naming route,
model, and level.

tsconfig.host.json

@@ -10,6 +10,7 @@
   "include": [
     "apps/web/tests/scaffold.ts",
     "apps/web/tests/default-model.e2e.ts",
+    "apps/web/tests/declared-reasoning.e2e.ts",
     "apps/web/tests/support.ts",
     "apps/web/tests/scaffold-hermetic.e2e.ts",
     "apps/web/tests/core-web-profile.snapshot.ts",