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/triage.rs

@@ -500,8 +500,8 @@ pub async fn run(
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::config::DeepseekConfig;
-    use crate::curate::llm::{MockBackend, UsageMeter};
+    use crate::config::ProviderConfig;
+    use crate::curate::llm::{MockBackend, PriceTable, UsageMeter};
     use crate::curate::prefilter::tests::article;
     use crate::curate::signals::{Neighbour, TopInterest};
     use crate::types::TokenUsage;
@@ -584,11 +584,11 @@ mod tests {
             r#"{"articles":[{"id":42,"interest":8,"kind":"essay","why":"first answer"}]}"#,
             TokenUsage::default(),
         );
-        let config = DeepseekConfig::default();
+        let config = ProviderConfig::deepseek();
         let llm = LlmClient::with_backend(
             &config.model,
             "profile".into(),
-            UsageMeter::new(&config, 10.0),
+            UsageMeter::with_prices(PriceTable::from(&config), 10.0),
             backend.clone(),
         );
         let pool = HashSet::from([42]);