fix(sf-from-source): switch from bun to node — clean from-source path

bun was the wrong runtime for our environment, two ways:

1. bun doesn't ship node:sqlite. sf-db.ts falls back through node:sqlite
   → better-sqlite3 → null. Result: 'No SQLite provider available' and
   degraded-mode filesystem-state derivation, even though sqlite is
   actually available (node:sqlite under node, bun:sqlite under bun —
   both valid, but our code only knows the node names).

2. bun's loader doesn't inherit the system library search path under
   Nix. libz.so.1 isn't found for forge_engine.node, so the native
   addon falls through to JS implementations (slower).

Both warnings ("Native addon not available", "DB unavailable —
degraded mode") were the symptom of "we're running under bun".

Fix: use node + the existing src/resources/extensions/sf/tests/
resolve-ts.mjs loader hook (which already handles .js → .ts
import-specifier remapping for runtime resolution) +
--experimental-strip-types (node 22+, native in 24).

Result: from-source via node loads cleanly. No native warning.
No sqlite warning. No degraded mode. Exec: `./bin/sf-from-source
--print "..."` returns the model output and nothing else.

Drops the LD_LIBRARY_PATH zlib-injection hack that was added in
4912f6ea8 — that was working around the bun native-loader issue
that doesn't exist under node.

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

bin/sf-from-source

@@ -1,19 +1,31 @@
 #!/usr/bin/env bash
 #
-# sf-from-source — run SF directly from this source checkout via bun.
+# sf-from-source — run SF directly from this source checkout via node.
 #
-# Purpose: every local commit in this repo (e.g. the #4251 fix) is live
-# immediately without reinstalling the bun-packaged sf-run. Subagents can
-# spawn sf by pointing SF_BIN_PATH at this script instead of dist/loader.js.
+# Purpose: every local commit in this repo is live immediately without
+# rebuilding dist/. Subagents can spawn sf by pointing SF_BIN_PATH at
+# this script instead of dist/loader.js.
+#
+# Why node, not bun:
+#   - bun doesn't ship node:sqlite (sf-db.ts falls back to filesystem-
+#     derivation degraded mode under bun).
+#   - bun's native-addon loader doesn't inherit the system library
+#     search path under Nix (libz.so.1 not found for forge_engine.node).
+#   - node 22.5+ has node:sqlite built-in; node 24 supports
+#     --experimental-strip-types so .ts runs directly.
+#   - The src/resources/extensions/sf/tests/resolve-ts.mjs loader hook
+#     already handles .js → .ts import-specifier remapping for runtime
+#     resolution.
 #
 # Contract:
-#   - Executable shim spawn() / exec() can launch directly.
+#   - Executable shim; spawn() / exec() can launch directly.
 #   - Exports SF_BIN_PATH before handing off to loader.ts so loader.ts's
 #     `SF_BIN_PATH ||= process.argv[1]` branch preserves the shim path
 #     instead of clobbering it with the .ts loader path (which is not
 #     directly executable by child_process.spawn).
 #
-# Requirements: bun on PATH, node_modules populated (`bun install` once).
+# Requirements: node >= 22.5 on PATH (24+ recommended for strip-types),
+# node_modules populated.
 set -euo pipefail
 
 SCRIPT_DIR=$(cd -- "$(dirname -- "$(readlink -f "${BASH_SOURCE[0]}")")" &>/dev/null && pwd)
@@ -21,17 +33,8 @@ SF_SOURCE_ROOT=$(cd -- "$SCRIPT_DIR/.." &>/dev/null && pwd)
 
 export SF_BIN_PATH="$SCRIPT_DIR/sf-from-source"
 
-# Native addon (forge_engine.node) links against libz / libstdc++ that are
-# resolved automatically when run under node, but bun's loader doesn't
-# inherit the same library search path under Nix. Prepend a Nix-store zlib
-# (and stdc++ where present) so require('forge_engine.linux-x64.node')
-# succeeds. No-op outside Nix (find returns nothing → empty prefix).
-if [ -d /nix/store ]; then
-	_sf_libz_dir=$(find /nix/store -maxdepth 4 -path '*-zlib-*/lib/libz.so.1' -printf '%h\n' 2>/dev/null | head -1)
-	if [ -n "${_sf_libz_dir:-}" ]; then
-		export LD_LIBRARY_PATH="${_sf_libz_dir}${LD_LIBRARY_PATH:+:$LD_LIBRARY_PATH}"
-	fi
-	unset _sf_libz_dir
-fi
-
-exec bun run "$SF_SOURCE_ROOT/src/loader.ts" "$@"
+exec node \
+	--import "$SF_SOURCE_ROOT/src/resources/extensions/sf/tests/resolve-ts.mjs" \
+	--experimental-strip-types \
+	--no-warnings \
+	"$SF_SOURCE_ROOT/src/loader.ts" "$@"