datalog: Phase 6 adornments + SIPS analysis (194/194)

New lib/datalog/magic.sx — first piece of magic-sets:

  dl-adorn-arg arg bound          → "b" or "f"
  dl-adorn-args args bound        → adornment string
  dl-adorn-goal goal              → adornment under empty bound set
  dl-adorn-lit lit bound          → adornment of any literal
  dl-vars-bound-by-lit lit bound  → free vars this lit will bind
  dl-init-head-bound head adn     → bound set seeded from head adornment
  dl-rule-sips rule head-adn      → ({:lit :adornment} ...) per body lit

SIPS walks left-to-right tracking the bound set; recognises `is` and
aggregate result-vars as new binders, lets comparisons and negation
pass through with computed adornments.

Inspection-only — saturator doesn't yet consume these. Lays
groundwork for a future magic-sets transformation.

10 new tests cover pure adornment, SIPS over a chain rule,
head-fully-bound rules, comparisons, and `is`. Total 194/194.

plans/datalog-on-sx.md

@@ -151,12 +151,17 @@ Naive bottom-up derives **all** consequences before answering. Magic sets
 rewrite the program so the fixpoint only derives tuples relevant to the
 goal — a major perf win for "what's reachable from node X" queries on
 large graphs.
-- [ ] Adornments: annotate rule predicates with bound (`b`) / free (`f`)
-      patterns based on how they're called.
+- [x] Adornments: `dl-adorn-goal goal` and `dl-adorn-lit lit bound` in
+      `lib/datalog/magic.sx`. Per-arg `b`/`f` based on whether the arg
+      is a constant or a variable already in the bound set.
 - [ ] Magic transformation: for each adorned predicate, generate a
       `magic_<pred>` relation and rewrite rule bodies to filter through it.
-- [ ] Sideways information passing strategy (SIPS): left-to-right by
-      default; pluggable.
+- [x] Sideways information passing strategy (SIPS): left-to-right
+      `dl-rule-sips rule head-adornment` walks body literals tracking
+      the bound set, returning `({:lit :adornment} ...)`. Recognises
+      `is`/aggregate result-vars as new binders; comparisons and
+      negation pass through with computed adornments. (Pluggable
+      strategies are future work.)
 - [x] `dl-set-strategy! db strategy` hook + `dl-get-strategy db`. Default
       `:semi-naive`. `:magic` accepted but the transformation itself is
       deferred — saturator currently falls back to semi-naive. Tests
@@ -284,6 +289,16 @@ large graphs.
 
 _Newest first._
 
+- 2026-05-08 — Phase 6 adornments + SIPS in
+  `lib/datalog/magic.sx`. Inspection helpers — `dl-adorn-goal` and
+  `dl-adorn-lit` compute per-arg `b`/`f` patterns under a bound
+  set; `dl-rule-sips rule head-adornment` walks body literals
+  left-to-right propagating the bound set, recognising `is` and
+  aggregate result-vars as new binders. Lays groundwork for a
+  later magic-sets transformation. 10 new tests cover pure
+  adornment, SIPS over a chain rule, head-fully-bound rules,
+  comparisons, and `is`. Saturator does not yet consume these.
+
 - 2026-05-08 — Comprehensive integration test in api suite: a
   single program exercising recursion (`reach` transitive closure)
   + stratified negation (`safe X Y :- reach X Y, not banned Y`) +