feat: quadrant-based model routing with per-slot provider cascades

docs/ROADMAP.org

@@ -386,10 +386,17 @@ Memory scope: ~:scope~ property on memory-objects (memex/session/project).
 Implement lazy-loading proxies for large-scale memory traversal.
 
 **** TODO Model-Tier Routing (cost optimization)
-Extend ~*model-selector-fn*~ for complexity-based routing.
-- Heartbeats → smallest model
-- User input → medium model
-- Complex reasoning → large model
+Extend ~*model-selector*~ for quadrant-based routing with per-slot provider cascades.
+- Privacy filter (local-only for @personal content) — top priority
+- Quadrant tagging (foreground/background × probabilistic/deterministic)
+- Complexity classifier (code/plan/chat/background slots), each with its own provider cascade
+- Model-selector skill registers into $*model-selector*$ hook
+
+Deferred:
+- Economics / budget tracking (per-request cost, cumulative caps)
+- TUI /config command for cascade configuration (env vars for now)
+- Skill metadata declaring complexity at defskill time (keyword-based for now)
+- Visual model indicator in TUI status bar
 
 **** TODO Memory Scope Segmentation
 Extend memory-object with ~:scope~ property.