feat(build): tune GHC for haskelseed (8 CPU / 30 GiB)

- .ghci: -j1 → -j4 for parallel module compilation
- scripts/compile-check: auto-detect high-RAM hosts (>16GB) and
  set GHCRTS="-A256m -M20g" to reduce GC pressure
- devenv.nix: update comment only (GHCRTS still set at runtime)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.ghci

@@ -1,9 +1,8 @@
 :set -XNoImplicitPrelude
 :def loadFromIHP \file -> (System.Environment.getEnv "IHP_LIB") >>= (\ihpLib -> readFile (ihpLib <> "/" <> file))
 :loadFromIHP applicationGhciConfig
--- Resource limit: override IHP's default -j (unlimited parallel) with -j1
--- on this constrained host (2 CPU / 3.8 GiB RAM).
-:set -j1
+-- haskelseed (8 CPU / 30 GiB RAM): allow parallel module compilation.
+:set -j4
 -- Report errors from all modules in one pass (don't stop at first failure).
 -- Critical for batch error fixing — see IHUB-WP-0016 C4.
 :set -fkeep-going

devenv.nix

@@ -22,7 +22,7 @@
   # ── Resource limits (constrained host: 2 CPU / ~3.8 GiB RAM) ─────────────
   # -A32m: smaller minor heap; -M2g: hard heap ceiling.
   # -N1 omitted: requires -threaded, which breaks IHP tools.
-  # GHC parallel module compilation is capped via -j1 in .ghci.
+  # GHC parallel module compilation is capped via -j4 in .ghci.
   env.GHCRTS = "-A32m -M2g";
 
   # ── IHP environment variables ─────────────────────────────────────────────

scripts/compile-check

@@ -2,7 +2,7 @@
 # scripts/compile-check — one-shot GHC compilation check.
 #
 # Does NOT start postgres or tailwind — just GHC.
-# Relies on .ghci (sets -j1, -fkeep-going, loads IHP config).
+# Relies on .ghci (sets -j4, -fkeep-going, loads IHP config).
 #
 # Usage:
 #   scripts/compile-check            # show errors in terminal + write log
@@ -30,6 +30,14 @@ echo "[compile-check] Log: $LOGFILE"
 echo "[compile-check] Mode: ${MODE:-interactive}"
 echo "[compile-check] IHP_LIB: $IHP_LIB"
 
+# Override GHC RTS for hosts with more RAM (e.g., haskelseed: 8 CPU / 30 GiB).
+# devenv.nix sets -M2g for constrained hosts; override here if available RAM is higher.
+TOTAL_RAM_MB=$(awk '/MemTotal/{print int($2/1024)}' /proc/meminfo 2>/dev/null || echo 0)
+if [[ "$TOTAL_RAM_MB" -gt 16000 ]]; then
+    export GHCRTS="-A256m -M20g"
+    echo "[compile-check] Host RAM: ${TOTAL_RAM_MB}MB — using GHCRTS=$GHCRTS"
+fi
+
 # One-shot compile: load all modules via .ghci config then quit immediately.
 # -fkeep-going (set in .ghci) ensures all errors are reported, not just the first.
 # ghcid is not available in this environment; ghci one-shot gives the same error output.