mod: Ext 13 — SLA sweep over pending lifecycle cases, 307/307

Composes lifecycle (Phase 3) with time (Ext 12): a timed-case pairs a case with
its state-entry tick; mod/overdue? flags pending cases (open/triaged/appealed)
past a deadline; mod/sla-sweep returns the breached report ids. Terminal states
never breach. Pure overlay — lifecycle stays timeless, caller stamps entry. +15 tests.

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

plans/mod-on-sx.md

@@ -16,7 +16,7 @@ federation extension.
 
 ## Status (rolling)
 
-`bash lib/mod/conformance.sh` → **292/292** (roadmap + 12 extensions complete)
+`bash lib/mod/conformance.sh` → **307/307** (roadmap + 13 extensions complete)
 
 ## Ground rules
 
@@ -147,6 +147,11 @@ lib/mod/fed.sx
   derivation goal-by-goal with `[proved]`/`[unproved]` marks and unification
   bindings. E.g. `Report rc: escalate (rule: repeated-escalate)` … `[proved]
   report(rc, B, S), report_count(S, N), N >= 3  {B=ann, N=3, S=dave}`.
+- [x] **Ext 13 — SLA sweep over pending cases** (`lib/mod/sla.sx`, +15). Composes
+  lifecycle (Phase 3) with time (Ext 12): a timed-case pairs a case with the tick
+  it entered its state; `mod/overdue?` flags pending cases (open/triaged/appealed)
+  past a deadline; `mod/sla-sweep` returns the breached report ids. Terminal states
+  never breach. Pure overlay — lifecycle stays timeless, the caller stamps entry.
 - [x] **Ext 12 — temporal burst detection** (`lib/mod/temporal.sx`, +15). Reports
   gain an `:at` tick (deterministic, supplied — never clock-read).
   `mod/decide-temporal now window` counts reports about the subject within
@@ -202,6 +207,11 @@ lib/mod/fed.sx
 
 ## Progress log
 
+- **Ext 13 — SLA sweep, 307/307** (+15). Two subsystems compose cleanly: lifecycle
+  states + temporal ticks → "which pending cases have sat too long". Kept lifecycle
+  pure by having the SLA layer carry entry-time externally (timed-case wrapper)
+  rather than stamping the case — same separation-of-concerns as keeping the state
+  machine out of Prolog.
 - **Ext 12 — temporal burst detection, 292/292** (+15). Adds the time dimension:
   a windowed count distinguishes a burst from slow accumulation, where the plain
   count rule cannot. Time is a supplied tick (`:at`), keeping everything