feat: add OpenRouter provider to golden harness, close Phase 0 gate

- provider-agnostic llm-client (grok + openrouter) with page-slug context
- live golden run scored and passing via x-ai/grok-4.6
- ADR 0010; spike docs flipped to done

docs/decisions/0010-openrouter-live-golden.md

@@ -0,0 +1,30 @@
+# 10. Golden harness scores live runs through a provider-agnostic LLM client (OpenRouter first)
+
+- **Status:** Accepted
+- **Date:** 2026-08-15
+
+## Context
+
+Phase 0's golden-task spike was the last gate item, stuck at "partial" because no `XAI_API_KEY` was set and the harness hard-coded `api.x.ai`. The developer holds an OpenRouter key, and OpenRouter speaks the same OpenAI-compatible `chat/completions` shape (including tool-calling), so the live run could be unblocked without a Grok-specific key.
+
+## Decision
+
+Replace the hard-coded `grok-client.ts` with a provider-agnostic `llm-client.ts` that supports `grok` (x.ai) and `openrouter`, selected by `LLM_PROVIDER`. The OpenRouter default model is `x-ai/grok-4.6`. The harness now passes the site's page slugs into the prompt.
+
+### Options considered
+
+- Wait for an `XAI_API_KEY` and keep the hard-coded x.ai client.
+- Hard-code OpenRouter, dropping the x.ai path.
+- Provider-agnostic client with `grok` + `openrouter` (chosen).
+
+### Rejected
+
+- Wait for x.ai — blocks the gate on a key we don't have, for no technical reason.
+- OpenRouter-only — the plan (IMPLEMENTATION §3) still names Grok the default adapter; keeping both providers matches that plan and costs one env switch.
+
+## Consequences
+
+- The live gate run is scored and passing (`gb-01` passed on `x-ai/grok-4.6`); the Phase 0 golden spike flips to done.
+- `x-ai/grok-latest` is not a callable OpenRouter ID (returns 400); the pinned `x-ai/grok-4.6` works and supports `tool_choice: required`.
+- A real finding: without the page-slug list in the prompt, the model guessed `page: "home"` and failed. Tool-call prompts must always carry site/page context. Sprint 3 must inherit this when it builds `api/src/agents/llm-client.ts`.
+- `llm-client.ts` here is a spike; Sprint 3 will generalize it (streaming, circuit breaker, fallback) rather than promote this file verbatim.

docs/decisions/README.md

@@ -23,6 +23,7 @@ Each ADR is a single file following the [Nygard format](https://cognitect.com/bl
 | [0007](0007-media-proxy-not-copy.md) | Sandboxes proxy uploads; never copy the media library | Accepted |
 | [0008](0008-empty-packages-not-stubs.md) | Workspace ships empty packages, not placeholder source | Accepted |
 | [0009](0009-repo-rename.md) | Repository renamed originmain → wursor | Accepted |
+| [0010](0010-openrouter-live-golden.md) | Golden harness scores live runs through a provider-agnostic LLM client (OpenRouter first) | Accepted |
 
 ## How to add one