feat: restore CI/release, prompt contracts, faster install (0.9.33)

Bring back Gitea CI + auto-publish; share release helpers; strengthen multi-turn
tool/job prompts with a unit contract; ccache/make help and --release bootstrap.

Co-authored-by: Cursor <cursoragent@cursor.com>

scripts/package_windows.sh

@@ -4,6 +4,8 @@
 # picks another, e.g. build-msys2) and busybox-w32.
 set -euo pipefail
 ROOT="$(cd "$(dirname "$0")/.." && pwd)"
+# shellcheck source=lib_release.sh
+. "$ROOT/scripts/lib_release.sh"
 REL="$ROOT/dist/windows-x86_64"
 if [[ -n "${CST_WIN_BUILD:-}" ]]; then
   EXE="$ROOT/$CST_WIN_BUILD/cst-agent.exe"
@@ -15,7 +17,7 @@ BB="$ROOT/third_party/busybox/busybox.exe"
 [[ -f "$EXE" ]] || { echo "no cst-agent.exe; build first" >&2; exit 1; }
 [[ -f "$BB" ]] || { echo "no busybox.exe; scripts/build_third_party_mingw.sh busybox-w32" >&2; exit 1; }
 
-ver="$(sed -n 's/^#define CST_VERSION_\(MAJOR\|MINOR\|PATCH\) \([0-9]*\)$/\2/p' "$ROOT/include/cst_version.h" | paste -sd.)"
+ver="$(cst_version)"
 strip="${MINGW_HOST-x86_64-w64-mingw32}"
 strip="${strip:+$strip-}strip"
 command -v "$strip" >/dev/null || strip=strip # MSYS2: unprefixed
@@ -33,7 +35,7 @@ echo "$ver" >"$REL/VERSION"
 zip="$ROOT/dist/cst-agent-$ver-windows-x86_64.zip"
 rm -f "$zip"
 (cd "$ROOT/dist" && zip -qr "$zip" windows-x86_64)
-(cd "$ROOT/dist" && sha256sum "$(basename "$zip")" >"$(basename "$zip").sha256")
+cst_sha256_write "$zip"
 ls -la "$REL"
 echo "$zip"
 
@@ -43,7 +45,7 @@ if command -v makensis >/dev/null; then
   rm -f "$setup"
   makensis -V2 -WX -INPUTCHARSET UTF8 -DVERSION="$ver" -DSRCDIR="$REL" \
     -DOUTFILE="$setup" "$ROOT/scripts/windows/cst-agent.nsi"
-  (cd "$ROOT/dist" && sha256sum "$(basename "$setup")" >"$(basename "$setup").sha256")
+  cst_sha256_write "$setup"
   echo "$setup"
 elif [[ "${CST_REQUIRE_NSIS:-0}" == 1 ]]; then
   echo "makensis not found" >&2