v0.5.0 - Correctness & Stability (Phase 1/6)

Phase 1 of the roadmap to v1.0.0: three concurrency bug fixes.

Behavior changes

• run_task_immediately() now raises TaskNotActiveError when the task is not active. Previously a running task could be dispatched a second time concurrently (breaking the no-overlap guarantee) and a paused task was silently un-paused. Resume paused tasks explicitly with resume_task().

What's new

• shutdown(timeout=...) / stop(timeout=...) — optional bound on how long shutdown waits for the scheduler thread and in-flight jobs. Jobs that do not exit within the deadline are abandoned on their worker threads with a warning, so a hung handler can no longer block application shutdown forever. Default (timeout=None) keeps the previous wait-forever behavior.
• New exception TaskNotActiveError (exported from quiv).

Fixes

• remove_task() racing the dispatch loop could raise a KeyError that stalled the scheduler for 5 seconds; dispatch now skips removed tasks gracefully, and the shared handler/callback/stop-event registries are protected by a lock.
• shutdown() now signals cancellation only to running jobs instead of scanning the entire retained job history.

Housekeeping

• Roadmap phases renumbered: v0.3.x/v0.4.x were already consumed by earlier feature releases, so Phase 1 ships as v0.5.0 and later phases shift down accordingly (Phase 6 stays v1.0.0).
• 7 new regression tests; docs, release notes, and AI-tooling artifacts updated; version bumped to 0.5.0.
• Docs cleanup: all Markdown files unwrapped to one paragraph per continuous line (zensical can break rendering when a sentence/paragraph is split across source lines). No content changes.