feat: foundations — canonical types, Parse grammar, env DSNs, health, chains

Phase 1 of the majordomo build:
- llm/ canonical contract (messages, parts, tools, capabilities, streaming,
  Model/Provider, error classification)
- health/ clock-injected tracker (threshold bench, exponential capped
  cooldown, reset-on-success)
- root Registry + Parse (verbatim model ids, inline recursive alias
  expansion with cycle detection, chain dedup), LLM_* env-DSN providers
  (go-llm parity: lazy fallback + eager LoadEnv), health-aware chain
  executor behind the Model interface
- provider/fake scriptable test provider; hermetic test suite incl. the
  trailing-thinking chain and foreman:// env loading
- ADRs 0001-0008, CLAUDE.md, README (honest matrix), CI workflow,
  docs/phase-1-design.md

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

docs/adr/0007-dependency-policy.md

@@ -0,0 +1,31 @@
+# ADR-0007: Dependency policy — stdlib-first, hand-rolled REST clients
+
+**Status:** Accepted — 2026-06-10
+
+## Context
+
+go-llm leans on SDKs (openai-go, go-anthropic, genai) and carries their
+transitive weight and churn. The kickoff mandates minimal dependencies with
+full control over multimodal payloads and capability handling.
+
+## Decision
+
+- **Hand-rolled `net/http` JSON clients** for OpenAI(+compatible),
+  Anthropic(+compatible), Ollama (cloud + local), and foreman. Their REST
+  surfaces are small and stable; owning the wire shapes gives exact control
+  over tool calls, structured output, streaming, and image payloads.
+- **One approved third-party dependency:** the official Google Gen AI Go SDK
+  (`google.golang.org/genai`) for the Gemini provider — Google's surface
+  moves too much to hand-roll profitably.
+- Image normalization uses stdlib `image`, `image/jpeg`, `image/png`.
+  `golang.org/x/image` may be added **only** if a needed format demands it,
+  via a new ADR.
+- Any other third-party dependency requires its own ADR justifying it.
+- No persistent store, no metrics stack, no config framework, no CLI beyond
+  `examples/` (out-of-scope guardrails).
+
+## Consequences
+
+- `go.mod` stays near-empty; consumers inherit almost nothing transitively.
+- We own wire-format drift: provider docs are verified against current
+  documentation at implementation time and recorded in the provider ADRs.