fix: keep self-learning alive after CLI exit

[EvanProgramming]

Fixes #158

What changed

• start one detached, per-workspace learning worker from the CLI
• keep the worker dormant while the CLI heartbeat is fresh, then dispatch bounded learning cycles after Ctrl-C, /quit, or terminal exit
• persist /self-learning feature switches in the authoritative SQLite store and reload them in the worker
• package the worker module and cover singleton spawn, stale-heartbeat dispatch, and restart-persistent flags

Validation

• python3.12 -m unittest tests.test_learning_worker -v
• focused distribution/install tests
• make lint
• git diff --check

The host-only make check import step requires the project dependencies; the dependency-complete CI run is the authoritative full-suite gate.