feat(run): rerun tasks when inputs change with --watch

[kdy1]

Motivation

vp run should keep tasks up to date as their inputs change, including restarting long-running commands. This implements the file-change-triggered task execution described in delinoio/oss#894.

Related reference: @cnakazawa's post on X.

Changes

• Add vp run --watch build: run immediately, then restart affected tasks and their dependents after input changes, keeping unrelated tasks running.
• Discover inputs while commands are still running through live file-access tracing. Reuse existing input patterns and exclusions, including when caching is disabled, and retain subscriptions on cache hits.
• Preserve dependency ordering and concurrency limits, coalesce changes, recover after task failures, and prevent canceled or invalidated executions from entering the cache.
• Stop process trees before restarting with Unix process groups and Windows Job Objects. Close task stdin, retain existing log modes, and clean up all tasks on Ctrl+C.
• Handle new files, deletions, renames, atomic saves, and directory reads; suppress restarts from a task's own outputs while propagating those changes to consumers.
• Document usage and limitations, update generated configuration types, and add regression coverage for scheduling, file events, caching, cancellation, and live tracing.

Task definitions and dependency relationships are fixed when watch starts. Existing dependency tasks must finish before their dependents run; service-readiness dependencies are outside this change.

AI disclosure

This implementation was developed with AI assistance from OpenAI Codex (GPT-6). The commits include an AI co-author trailer.