In manual sessions (no auto-mode), bootstrapAutoSession never runs, so the
GSD database is never opened. This causes gsd_save_decision,
gsd_update_requirement, and gsd_save_summary tools to always fail with
'GSD database is not available'.
Add ensureDbOpen() helper that checks isDbAvailable() first, then tries to
open the DB from the expected .gsd/gsd.db path if it exists. All three tool
handlers now use this helper instead of the check-only pattern.
The fix is backward-compatible: in auto-mode the DB is already open, so
ensureDbOpen() returns true immediately on the isDbAvailable() check.
f2bcd049ae