feat: OpenAI, Anthropic, and native-Ollama providers + media pipeline

Phase 3:
- provider/openai: Chat Completions for OpenAI + compat endpoints (SSE
  streaming with by-index tool-call assembly, response_format json_schema,
  legacy max_tokens option, reasoning_effort)
- provider/anthropic: Messages API (tool_use/tool_result, GA structured
  output via output_config.format, full SSE event parser, 529 transient)
- provider/ollama: one native /api/chat client behind the ollama,
  ollama-cloud, and foreman built-ins (presets; NDJSON streaming tolerant
  of foreman's buffered single-object responses; object tool arguments;
  format-schema structured output; think mapping)
- media/: capability normalization (sniff, downscale, transcode, byte
  ladder, ErrUnsupported), wired into the chain executor per target with
  penalty-free advance past incapable elements
- registry: real provider + scheme wiring, WithHTTPClient option, required
  env-foreman TLS chat round-trip test
- ADR-0009 multimodal strategy, ADR-0010 tools/structured mapping; README
  matrix + CLAUDE.md synced

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

registry.go

@@ -2,6 +2,7 @@ package majordomo
 
 import (
 	"fmt"
+	"net/http"
 	"os"
 	"strings"
 	"sync"
@@ -73,11 +74,12 @@ func (c ChainConfig) classify(err error) llm.ErrorClass {
 }
 
 type registryConfig struct {
-	health    health.Config
-	chain     ChainConfig
-	envLookup func(string) string
-	environ   func() []string
-	skipEnv   bool
+	health     health.Config
+	chain      ChainConfig
+	envLookup  func(string) string
+	environ    func() []string
+	skipEnv    bool
+	httpClient *http.Client
 }
 
 // RegistryOption configures New.
@@ -115,6 +117,14 @@ func WithoutEnvProviders() RegistryOption {
 	return func(rc *registryConfig) { rc.skipEnv = true }
 }
 
+// WithHTTPClient sets the HTTP client used by built-in providers and
+// env-DSN scheme factories created by this registry (proxies, custom TLS,
+// test servers). Providers registered explicitly via RegisterProvider keep
+// whatever client they were built with.
+func WithHTTPClient(c *http.Client) RegistryOption {
+	return func(rc *registryConfig) { rc.httpClient = c }
+}
+
 // New creates a Registry with all built-in providers and scheme factories
 // registered, then loads LLM_* env-DSN providers from the process
 // environment (unless WithoutEnvProviders is given). Malformed LLM_* entries
@@ -139,7 +149,7 @@ func New(opts ...RegistryOption) *Registry {
 		envLookup: cfg.envLookup,
 	}
 
-	registerBuiltins(r)
+	registerBuiltins(r, cfg.httpClient)
 
 	if !cfg.skipEnv {
 		env := make(map[string]string)