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>

CLAUDE.md

@@ -27,9 +27,15 @@ majordomo        Registry, Parse, env-DSN loading, chain executor, re-exports
   llm/           canonical contract: Message/Part/Request/Response/Option,
                  Tool/Toolbox, Capabilities, Stream, Model, Provider, errors
   health/        clock-injected health tracker (bench/backoff)
-  media/         image normalization to target capabilities   (Phase 3)
+  media/         image normalization to target capabilities (sniff real
+                 format, downscale, transcode, byte ladder; ErrUnsupported
+                 for what can't fit) — chains normalize PER TARGET
   provider/fake/ scriptable in-memory provider for hermetic tests
-  provider/{openai,anthropic,ollama,google}/                  (Phases 3-4)
+  provider/openai/    Chat Completions client (+ all OpenAI-compat targets)
+  provider/anthropic/ Messages API client (+ Anthropic-compat targets)
+  provider/ollama/    one native /api/chat client serving the ollama,
+                      ollama-cloud, and foreman built-ins via presets
+  provider/google/    Gemini on the official genai SDK         (Phase 4)
   agent/         Agent run loop                               (Phase 5)
   skill/         Skill interface + composition                (Phase 6)
   examples/      one runnable example per hard requirement    (Phase 7-8)