v0.6.3 — Adversarial QA: 9 bug fixes

Bug Fixes

• Corrupted DB: open_db() now catches sqlite3.DatabaseError and prints a user-friendly error instead of crashing (#326)
• Loop validation: loop start --max-iters 0 or negative values now rejected with clear error (#327)
• Cron range validation: validate_cron_expression now checks field value ranges (e.g. minute 0-59) (#328)
• Cron duplicate names: Adding a cron job with a duplicate name now errors instead of silently inserting (#329)
• Cron @Aliases: @reboot, @daily, @weekly, @monthly, @hourly etc. now accepted as valid schedules (#330)
• notify add --json: notify add now accepts --json and emits structured output (#331)
• route-fallback same model: Rejected when primary == fallback (#332)
• diff-context --json outside git: Now emits a JSON error object instead of empty stdout (#333)
• split plan empty task: Empty task string is now rejected (#334)