Curation v2 step 7: cleanup, prune paths, implementation notes

Dead code and stale v1 comments removed (clippy -W dead_code clean, the
three world.rs warnings fixed), the Brief chapter's TOC title renamed from
"From the Editor", features prune now also sweeps article_assessments and
generate runs the sweep once after publishing, the example config is
tested key-for-key against Config::default(), README commands match
--help, and docs/plans/2026-08-15-implementation-notes.md records the
Anthropic and Voyage facts, the new tables, the budget-day rule and the
lock.

Implemented by a Claude agent from docs/plans/curation-v2-briefs/step7.md.

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

src/pipeline.rs

@@ -254,6 +254,9 @@ pub async fn generate(config: &Config, db: &Db, opts: &GenerateOptions) -> Resul
     };
 
     db.finish_run(run_id, &report).await?;
+    if stages.published.is_some() {
+        prune_retention(config, db).await;
+    }
     // The issue row is written before the report is costed, so stamp the finished
     // report onto it now (the paths are preserved by `COALESCE`, §3.13).
     if !opts.dry_run
@@ -282,6 +285,28 @@ pub async fn generate(config: &Config, db: &Db, opts: &GenerateOptions) -> Resul
     })
 }
 
+/// The retention sweep of `features prune` (§7.1, §7.4), run once per
+/// published issue. Best effort: a failure is logged and never touches the run.
+async fn prune_retention(config: &Config, db: &Db) {
+    let ranking = &config.curation.ranking;
+    match telemetry::prune(
+        db,
+        ranking.embedding_retention_days,
+        ranking.telemetry_retention_days,
+        Timestamp::now(),
+    )
+    .await
+    {
+        Ok(pruned) => tracing::info!(
+            embeddings = pruned.embeddings,
+            candidate_rows = pruned.telemetry,
+            assessments = pruned.assessments,
+            "retention prune complete"
+        ),
+        Err(error) => tracing::warn!(%error, "retention prune failed; continuing"),
+    }
+}
+
 /// What [`run_stages`] hands back; [`generate`] pairs it with the costed report.
 #[derive(Debug)]
 struct StageOutput {
@@ -1044,10 +1069,11 @@ async fn record_issue(db: &Db, issue: &Issue, published: &Published) -> Result<(
     Ok(())
 }
 
-/// Build the DeepSeek client, running the weekly profile rebuild when it is due.
+/// Build the bulk (DeepSeek) and editor (Claude) clients, running the weekly
+/// profile rebuild when it is due.
 ///
-/// Returns `None` for `--skip-llm` and for every configuration/API problem: the
-/// caller then curates heuristically instead of failing the run (§3.6).
+/// Each client is `None` for `--skip-llm` and for every configuration/API
+/// problem: the pipeline then degrades per §17 instead of failing the run.
 async fn build_llms(
     ctx: &StageContext<'_>,
     bulk_meter: &UsageMeter,