llm/ollama: disable thinking so reasoning models return content

Qwen 3.5 — the spec's recommended model — is a reasoning model. With
thinking on, Ollama streams its chain-of-thought into a separate
`thinking` field and hits num_predict before emitting any answer into
`content`, so Complete() got an empty string and the checkpoint failed
with "no JSON object in model output". Sending `"think": false` on every
/api/chat request fixes it; non-thinking models (qwen2.5) ignore the flag.

Validated end-to-end on deployment hardware (Ollama, qwen3.5:9b): the
grammar checkpoint now caught all five ESL errors in a 3-sentence sample
with correct JSON and string-anchoring, ~8.5s warm.

Claude-Session: https://claude.ai/code/session_016Yr6jELuRc7hyzYLccQKZd

BUILD_PLAN.md

@@ -7,6 +7,7 @@ Multi-session build. **Source of truth for what's done and what's next.** Update
 - **Copyleaks deferred** — needs a public webhook; skip Tier-2 plagiarism until there's a public endpoint. Tier-1 voice-consistency (local) is in scope.
 - **Traefik/deploy deferred** — local dev first.
 - **LLM**: Qwen 3.5 (256K context) on 64GB dual-GPU. Grammar checkpoint cap ~10K tokens (latency guard); voice pass sends whole document.
+  - **Reasoning models**: the Ollama client sends `"think": false` on every request. Qwen 3.5 is a reasoning model — left on, it streams chain-of-thought into a separate `thinking` field and exhausts `num_predict` before emitting any answer in `content` (empty response). Non-thinking models ignore the flag. (Validated on deployment hardware 2026-06-25.)
 - **Suggestion anchoring**: resolve by `original` string in ProseMirror coords at render time; stored `from_pos`/`to_pos` are plaintext offsets for server-side use only. (Spec Note #6.)
 - **Aesthetic is an acceptance criterion**: pretty, warm, Chinese-woman-friendly; CJK fonts first-class.