feat: add DeepSeek, Moonshot, xAI, Groq, Ollama; drop v1; migrate TUI to v2

Five OpenAI-compatible providers join the library as first-class constructors
(llm.DeepSeek, llm.Moonshot, llm.XAI, llm.Groq, llm.Ollama). Their wire-level
implementation is shared via a new v2/openaicompat package which is the
extracted guts of the old v2/openai provider; each provider supplies its own
Rules value to declare per-model constraints (e.g., DeepSeek Reasoner rejects
tools and temperature, Moonshot/xAI accept images only on *-vision* models,
Groq rejects audio input). v2/openai itself becomes a thin wrapper that sets
RestrictTemperature for o-series and gpt-5 models.

A new provider registry (v2/registry.go) exposes llm.Providers() and drives
the TUI's provider picker so adding a provider in future is a single-file
change.

The TUI at cmd/llm was migrated from v1 to v2 and moved to v2/cmd/llm. With
nothing else depending on v1, the v1 code at the repo root (all .go files,
schema/, internal/, provider/, root go.mod/go.sum) is deleted.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

v2/constructors.go

@@ -2,8 +2,13 @@ package llm
 
 import (
 	anthProvider "gitea.stevedudenhoeffer.com/steve/go-llm/v2/anthropic"
+	deepseekProvider "gitea.stevedudenhoeffer.com/steve/go-llm/v2/deepseek"
 	googleProvider "gitea.stevedudenhoeffer.com/steve/go-llm/v2/google"
+	groqProvider "gitea.stevedudenhoeffer.com/steve/go-llm/v2/groq"
+	moonshotProvider "gitea.stevedudenhoeffer.com/steve/go-llm/v2/moonshot"
+	ollamaProvider "gitea.stevedudenhoeffer.com/steve/go-llm/v2/ollama"
 	openaiProvider "gitea.stevedudenhoeffer.com/steve/go-llm/v2/openai"
+	xaiProvider "gitea.stevedudenhoeffer.com/steve/go-llm/v2/xai"
 )
 
 // OpenAI creates an OpenAI client.
@@ -46,3 +51,69 @@ func Google(apiKey string, opts ...ClientOption) *Client {
 	_ = cfg // Google doesn't support custom base URL in the SDK
 	return NewClient(googleProvider.New(apiKey))
 }
+
+// DeepSeek creates a DeepSeek client (OpenAI-compatible).
+//
+// Example:
+//
+//	model := llm.DeepSeek("sk-...").Model("deepseek-chat")
+func DeepSeek(apiKey string, opts ...ClientOption) *Client {
+	cfg := &clientConfig{}
+	for _, opt := range opts {
+		opt(cfg)
+	}
+	return NewClient(deepseekProvider.New(apiKey, cfg.baseURL))
+}
+
+// Moonshot creates a Moonshot AI (Kimi) client (OpenAI-compatible).
+//
+// Example:
+//
+//	model := llm.Moonshot("sk-...").Model("kimi-k2-0711-preview")
+func Moonshot(apiKey string, opts ...ClientOption) *Client {
+	cfg := &clientConfig{}
+	for _, opt := range opts {
+		opt(cfg)
+	}
+	return NewClient(moonshotProvider.New(apiKey, cfg.baseURL))
+}
+
+// XAI creates an xAI (Grok) client (OpenAI-compatible).
+//
+// Example:
+//
+//	model := llm.XAI("xai-...").Model("grok-2")
+func XAI(apiKey string, opts ...ClientOption) *Client {
+	cfg := &clientConfig{}
+	for _, opt := range opts {
+		opt(cfg)
+	}
+	return NewClient(xaiProvider.New(apiKey, cfg.baseURL))
+}
+
+// Groq creates a Groq client (OpenAI-compatible).
+//
+// Example:
+//
+//	model := llm.Groq("gsk-...").Model("llama-3.3-70b-versatile")
+func Groq(apiKey string, opts ...ClientOption) *Client {
+	cfg := &clientConfig{}
+	for _, opt := range opts {
+		opt(cfg)
+	}
+	return NewClient(groqProvider.New(apiKey, cfg.baseURL))
+}
+
+// Ollama creates a client for a local Ollama instance (OpenAI-compatible).
+// No API key is required. Use WithBaseURL to point at a non-default host/port.
+//
+// Example:
+//
+//	model := llm.Ollama().Model("llama3.2")
+func Ollama(opts ...ClientOption) *Client {
+	cfg := &clientConfig{}
+	for _, opt := range opts {
+		opt(cfg)
+	}
+	return NewClient(ollamaProvider.New("", cfg.baseURL))
+}