feat(llm): add DeepSeek as first-class cloud provider (#204)

[ProfSynapse]

Summary

Adds DeepSeek as a direct cloud provider (alongside OpenAI / Anthropic / Google / Mistral / Groq / OpenRouter / etc.). Resolves #204.

DeepSeek's API is OpenAI-compatible, so the adapter is structurally a Groq-clone that plugs into the existing two-sided thinking abstraction (ThinkingEffortMapper for input, unified StreamChunk.reasoning for output) — the chat UI renders DeepSeek reasoning blocks for free, exactly like Claude / o-series / Gemini / Groq today.

Models

Model	Context	Max output	Pricing (in / out per 1M)	Cache hit
deepseek-v4-flash	1M	384K	$0.14 / $0.28	$0.0028
deepseek-v4-pro	1M	384K	$0.435 / $0.87 (75% off until 2026-05-31)	discounted

Each ships with a -thinking variant. Thinking mode uses DeepSeek's proprietary thinking: { type: "enabled", reasoning_effort: "high" \| "max" } request shape (NOT OpenAI's reasoning.effort), and surfaces reasoning via delta.reasoning_content (streaming) or message.reasoning_content (non-streaming). The unified ThinkingEffortMapper.getDeepSeekParams handles request-side translation; the adapter's stream extractor maps reasoning_content → StreamChunk.reasoning.

What changed

• New: DeepSeekAdapter.ts (375 LoC), DeepSeekModels.ts (111 LoC), DeepSeekAdapter.test.ts (275 LoC, 18 tests)
• Wired through 13 touchpoints: SupportedProvider union, AdapterRegistry, ProviderTypes defaults, ProviderManager def, ValidationService, ThinkingEffortMapper (incl. ProviderThinkingConfig interface + supportedProviders list), platform.ts mobile-compatible list, ModelDropdownRenderer, ProviderUtils (display name, color, emoji, abbreviation, streaming/functions/JSON lists), ProvidersTab (+cloudIds), VisionMessageFormatter, ingestTool labels
• frequency_penalty / presence_penalty are stripped from outgoing requests (DeepSeek removed support)
• Mobile-compatible (uses requestUrl-backed REST transport)

Test plan

• npx jest tests/services/llm/adapters/deepseek — 18/18 passing
• npx tsc --noEmit — clean
• npm run build — clean
• Manual smoke: enter API key in Settings → Providers → DeepSeek, send a message with deepseek-v4-flash, send a tool-using message with deepseek-v4-flash-thinking, verify reasoning block renders in the chat UI

Follow-ups (not blocking)

• ProviderManager.ts (659 LoC) and ProvidersTab.ts (645 LoC) crossed the 600-line maintainability threshold from the wiring additions. Both are pre-existing tech-debt watch items — refactor when next touched, not as part of this PR.

🤖 Generated with Claude Code

[ProfSynapse]

Follow-up: v5.8.15 (just released — https://github.com/ProfSynapse/nexus/releases/tag/5.8.15) fixes a wiring miss from this PR that prevented the DeepSeek models from appearing in the model dropdown even with a valid API key.

The 13 touchpoints listed above were all real, but two central aggregators were missed:

• src/services/StaticModelsService.ts — the UI's source of truth (getAllModels, getModelsForProvider, getAvailableProviders whitelist) had no deepseek entries, so getModelsForProvider('deepseek') hit the default: return [] branch.
• src/services/llm/adapters/ModelRegistry.ts — AI_MODELS and DEFAULT_MODELS records were both missing the deepseek key.

Fix in commit 4a35280 (10 lines across the 2 files). Note for the next provider addition: the "13 wiring touchpoints" checklist should include these two aggregators — they're the gate everything else flows through.

cc @surill (#204) — the v5.8.15 release on Obsidian Community Plugins / direct download now actually surfaces the models. Please grab the new build and report back if the dropdown still misbehaves.

[surill]

你好，我更新了v5.9.0，DeepSeek模型已经可以正常获取模型列表，目前对话功能已经可以正常使用，但是调用工具出现了问题，返回错误：❌ Tool execution failed: streaming generation failed with HTTP 400