Prepare v0.0.1: recoverable local execution for Linux

[tcballard]

Spool needs a runnable preview for testing on an Omarchy XPS. This adds explicit command execution with persistent workspaces and recovery that stops when an outcome is uncertain.

Changes:

• SQLite operation state machine, append-only evidence, versioned migration and exclusive journal ownership.
• Offline bubblewrap execution, per-job files, 60-second default timeout and capped captured output.
• Queue, exec, resume, recover, resolve, events, doctor and version commands.
• Crash tests covering four interruption points; legacy migration and lock ownership tests.
• XPS install/acceptance instructions, smoke script, Apache-2.0 license and CI-built x86_64 archive/checksum.

Validation: seven local tests pass, including subprocess crash recovery; formatting and Clippy pass; release archive builds. The local container denies bubblewrap network namespace creation, so real sandbox execution is a required CI check and remains unverified on Omarchy until XPS acceptance. No model/MCP/Core integration or disk/memory/process quotas are claimed.

This prepares a v0.0.1 candidate; it does not tag or publish a release. See docs/v0.0.1.md for the publication checklist.