Add Claude Agent SDK autopilot backend

[drafael]

Summary

• add a distinct same-instance claude-agent-sdk implementation backend while retaining direct claude-code review
• bind one explicit SDK installation, child, query, session, and caller-selected user-message UUID with isolated configuration and cooperative tool fencing
• require exact result/interrupt evidence, map continuity loss to EXECUTION_STATE_UNKNOWN, and await bounded cleanup
• register charter, doctor, generated runtime, documentation, and focused contract coverage

Validation

• npm run typecheck
• npm run lint
• npm run format:check
• npm test — 253 tests, 251 passed, 2 macOS platform skips
• npm run test:coverage — 33.21% overall lines; 89.10% for the compiled Agent SDK adapter
• deterministic dist/ comparison
• npm pack --dry-run --json and native/package inventory
• live Agent SDK 0.3.260 / Claude Code 2.1.260 completion and exact aborted_tools cancellation
• direct Claude Code 2.1.251 edit and exact-tree review
• final independent Codex review found no actionable correctness defects

Boundaries

• the SDK and matching executable remain explicitly operator-supplied and are never installed or discovered from private caches
• same-instance guarantees do not survive coordinator/query/process loss; unknown execution is never replaced automatically
• Windows remains cooperative and does not claim descendant containment