refactor(routes): drop prod-dead compile_routes; document disabled-shadow (§11 tail review)

Two review findings.

1. After R3 every production rebuild path uses `compile_effective_routes`;
   `compile_routes` (the old app-only compile) was called only by its own
   two unit tests, and its "runs in build_app" doc was stale — so the
   lenient-skip + disabled-drop regression guards no longer covered the
   live path. Remove `compile_routes` + its re-export, fold the lenient-skip
   rationale onto `compile_one`, and port both guards to
   `compile_effective_routes` (app-only rows are just depth-0 effective
   rows). Add a third guard pinning nearest-owner shadowing at the pure-
   compile layer. Fix the stale `compile_routes` mention in apply_service.

2. Document the disabled + inherited semantic: the `enabled` filter runs
   before the shadow check, so a disabled own-route does not claim its
   binding and an enabled ancestor template at the same path falls through
   ("disabled = absent", §4.3). Recorded on `compile_effective_routes` and
   in design §4.5 — the corollary (can't 404 an inherited route by
   disabling a same-path own route) points at the deferred per-app opt-out.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/manager-core/src/apply_service.rs

@@ -2111,8 +2111,8 @@ impl ApplyService {
         for r in &bundle.routes {
             reject_reserved_path(&r.path)?;
             // Structural validity (parity with the interactive route API):
-            // a route whose path/host doesn't parse would otherwise be
-            // written and then silently dropped by `compile_routes`.
+            // a route whose path/host doesn't parse would otherwise be written
+            // and then silently dropped by the route-table compile.
             pattern::parse_path(r.path_kind, &r.path)
                 .map_err(|e| ApplyError::Invalid(format!("route path `{}`: {e}", r.path)))?;
             pattern::parse_host(r.host_kind, &r.host, r.host_param_name.as_deref())