feat: add supervisor-helper.sh with SQLite schema and state machine (t128.1)

Implements t128.1 - Autonomous Supervisor SQLite schema and state machine.

- SQLite schema: tasks, batches, batch_tasks, state_log tables
- State machine: queued->dispatched->running->evaluating->complete/blocked/failed
- Retry cycle: evaluating->retrying->dispatched with configurable max retries
- Commands: init, add, batch, transition, status, list, next, reset, cancel, db
- Concurrency-aware dispatch via next command with batch limits
- State transition validation with audit log
- JSON output support for programmatic consumption
- Zero ShellCheck violations

Author: marcusquinn