feat: claude-code backends + llamaswap provider + dogfood the CC engine (#3)

Phase 2: bump majordomo to latest and wire its new llamaswap provider
into gadfly's endpoint switches; add claude-code/sonnet to gadfly's own
dogfood swarm (pin :sha-86f12c1, map CLAUDE_CODE_OAUTH_TOKEN) so the
Phase-1 engine runs as a live competitor; document the Ollama-through-CC
ANTHROPIC_BASE_URL proxy path as example-only.

The 11-model swarm (incl. claude-code/sonnet) reviewed it; 52 findings
graded via the MCP. Folded in the two real ones: a llamaswap
endpointProvider test (caught by claude-code/sonnet, citing CLAUDE.md)
and adding "openai-compatible" to the provider error messages (gpt-oss).

gofmt clean, go vet quiet, go build + go test -race green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Co-authored-by: Steve Dudenhoeffer <steve@stevedudenhoeffer.com>
Co-committed-by: Steve Dudenhoeffer <steve@stevedudenhoeffer.com>

README.md

@@ -66,6 +66,7 @@ majordomo failover chain / alias) is used verbatim.
 | **Ollama Cloud** (default) | `ollama-cloud` | `OLLAMA_API_KEY` / `OLLAMA_CLOUD_API_KEY` | ✅ in active use |
 | **Local Ollama** | `ollama` | none (`OLLAMA_HOST` or `GADFLY_BASE_URL` for a remote daemon) | ✅ tested |
 | **[foreman](https://gitea.stevedudenhoeffer.com/steve/foreman)** (native-Ollama queue daemon) | `foreman` + `GADFLY_BASE_URL`, or a `GADFLY_ENDPOINT_*` / `LLM_*` `foreman://` entry | optional bearer (via the endpoint/DSN) | ✅ native-Ollama path |
+| **llamaswap** (llama-swap model router) | `llamaswap` + `GADFLY_BASE_URL`, or a `GADFLY_ENDPOINT_*` entry | optional bearer | ⚠️ wired, **untested** |
 | **OpenAI-compatible** (incl. local Ollama's `/v1`) | `openai` + `GADFLY_BASE_URL` | `OPENAI_API_KEY` (any non-empty for Ollama) | ✅ tested against Ollama |
 | **OpenAI** | `openai` | `OPENAI_API_KEY` | ⚠️ wired, **untested** |
 | **Anthropic** | `anthropic` | `ANTHROPIC_API_KEY` | ⚠️ wired, **untested** |
@@ -115,11 +116,19 @@ Auth is read from the environment: the default is a **Pro/Max subscription** via
 > token + `PATH`/`HOME`/locale/`GADFLY_CLAUDE_*`), not the runner's full env, so the
 > Gitea token and provider keys aren't handed to the CLI.
 
-> **Untested, like the cloud providers.** This wires the CLI in and is exercised by its unit
-> tests, but a live subscription-auth run hasn't been validated end-to-end here — and using
-> subscription auth in automated CI is a gray area in Anthropic's terms. `auto` specialist
-> selection and the `delegate_investigation` worker are majordomo-only and are skipped with this
-> engine (Claude Code does its own legwork).
+**Alternate backends (example only, not validated here).** Because the subprocess env forwards
+`ANTHROPIC_*` and `CLAUDE_*`, you can point the same engine at a non-Anthropic backend by setting
+`ANTHROPIC_BASE_URL` (and `ANTHROPIC_AUTH_TOKEN`/`ANTHROPIC_API_KEY`) to an **Anthropic-API-compatible
+proxy** — e.g. [claude-code-router](https://github.com/musistudio/claude-code-router) or LiteLLM in
+front of Ollama — to run *Ollama models through Claude Code's harness* and compare it against the
+native majordomo loop. Whether tool-use survives a given proxy/backend varies, so this is documented
+as an example, not wired or tested here.
+
+> **The Pro/Max path is dogfooded but otherwise lightly tested.** `claude-code/sonnet` now runs on
+> gadfly's own PRs (see `.gitea/workflows/adversarial-review.yml`), but treat the engine as new —
+> and note that subscription auth in automated CI is a gray area in Anthropic's terms. `auto`
+> specialist selection and the `delegate_investigation` worker are majordomo-only and are skipped
+> with this engine (Claude Code does its own legwork).
 
 ### Endpoint aliases via env vars