Provider-agnostic LLM registry, config check, migration runbook

[llm] assigns the bulk and editor roles by name over a [providers.*]
registry (kind = openai | anthropic, per-provider model, effort, daily
ceiling and price table); DeepseekBackend becomes OpenAiCompatibleBackend
(reasoning_effort passthrough), AnthropicBackend builds from the same
ProviderConfig, meters and provider_costs are keyed by provider name.
Gemini 3.8 Flash is declared via Google's OpenAI-compatible endpoint so
switching the editor is one line (or DAILY_EPUB_LLM__EDITOR=gemini for an
A/B dry run). Stale [deepseek]/[anthropic] tables, the top-level
max_daily_usd and the old key env vars fail loudly.

daily-epub config check validates and prints the resolved roles, models,
key presence and paths without opening the database.

docs/runbooks/curation-v2-migration.md walks the server upgrade from v1.

Registry implemented by a Claude agent from an orchestrator brief;
verified fmt/clippy(-W dead_code)/test green.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01A1rCLQeKBgnBo3oTgHuTMe

src/curate/mod.rs

@@ -39,7 +39,7 @@ pub struct Curator {
 impl Curator {
     /// An empty [`llm::Llms`] corresponds to `--skip-llm`: cheap-signal order is
     /// used for selection and feed excerpts stand in for summaries (notes §6).
-    /// With only `bulk`, every editor call runs on DeepSeek (§4.2).
+    /// With only `bulk`, every editor call runs on the bulk provider (§4.2).
     pub fn new(config: Config, db: Db, llms: llm::Llms) -> Self {
         Self { config, db, llms }
     }
@@ -67,15 +67,15 @@ impl Curator {
         assess::run(
             &self.db,
             Some(bulk),
-            &self.config.deepseek.model,
+            &bulk.model,
             candidates,
-            self.config.deepseek.deep_batch_size,
-            self.config.deepseek.max_concurrent_requests,
+            self.config.llm.deep_batch_size,
+            bulk.max_concurrent_requests,
             self.config.curation.ranking.assessment_reuse_days,
             rescore,
             profile_version,
             assessed_at,
-            self.config.deepseek.score_temperature,
+            self.config.llm.score_temperature,
             &self.config.curation.sections,
         )
         .await
@@ -137,7 +137,7 @@ impl Curator {
             &self.llms,
             lineup,
             &self.config.editorial,
-            self.config.deepseek.editorial_temperature,
+            self.config.llm.editorial_temperature,
         )
         .await)
     }