plans: SX review master remediation plan + evidence

Consolidates the three-lane review (core K01-K110, hosts J*/C*/JS*/P*/S*,
conformance F1-F15) into plans/sx-review/:
- PLAN.md — 15 workstreams, phased execution, full per-finding coverage
  ledger (every ~213 finding-instances mapped to a workstream + status)
- RULINGS.md — 40 draft normative rulings (Phase-0 gate)
- core.md / hosts.md / conformance.md — the lane evidence files

dc7aa709 quick-wins batch marked DONE in the ledger; K01 (guard re-raise
hang), S1 (live HTTP crash), K03 (shift-k), and W14 (test gate) flagged as
the highest-value open work.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

plans/sx-review/README.md

@@ -0,0 +1,21 @@
+# SX Review — 2026-07-03
+
+Findings from three parallel review sessions of the SX language/runtime, plus the master
+remediation plan.
+
+| File | What |
+|------|------|
+| **PLAN.md** | Master remediation plan: 15 workstreams (W1–W15), execution order, and a full per-finding coverage ledger. Start here. |
+| **RULINGS.md** | 40 draft normative rulings (R1–R40). Phase-0 gate — ratify before the semantics fixes. |
+| core.md | Language core / spec semantics lane (K01–K110). |
+| hosts.md | Per-host implementations + FFI lane (J*, C*, JS*, P*, S*, PY). |
+| conformance.md | Cross-host agreement + test adequacy lane (F1–F15, S1–S5). |
+
+**Status:** the quick-wins batch (commit dc7aa709) landed 13 fixes + 4 partials; suite at baseline
+5762p/274f (fail set byte-identical). Everything else is OPEN/GATE/DEFERRED per PLAN.md's ledger.
+
+**Highest-value open items:** K01 (guard/handler re-raise hang — DoS-able, server+browser),
+S1 (live HTTP crash under load), K03 (shift-k double-execution), and W14 (test gate — the enabler
+that makes all other fixes verifiable).
+
+**Blocking decisions (maintainer):** D1 host lineup, D2 ratify rulings, D3 gate definition.