feat: add experimental acpx flows runtime and examples

[osolmaz]

Summary

• add an experimental acpx/flows runtime and flow run <file> for TypeScript workflow modules
• add generic flow primitives for ACP steps, local computation, checkpoints, and runtime-owned actions
• add per-step cwd, live run state, timeouts, JSON helpers, and file-backed flow persistence under ~/.acpx/flows/runs
• add shipped flow examples under examples/flows/, including a larger PR-triage example with a colocated written workflow description
• refactor the flow, queue, and CLI internals so the new surface stays maintainable
• document the flow model consistently across the README, CLI docs, architecture doc, examples, and skills/acpx/SKILL.md

Notes

• the core flow surface stays generic; workload-specific behavior is shown as an example flow rather than being baked into the CLI
• example workflows can perform real side effects if run against live repositories

Validation

• pnpm run check
• pnpm run check:docs
• source and built smoke runs against the shipped flow examples during development

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Reorder built-in agent examples to required precedence

AGENTS.md makes built-in agent ordering mandatory in examples (pi, openclaw, codex, claude, ...), but this new example lists codex before openclaw, which violates that required precedence. Because this ordering rule is a documented repo policy (not optional style), leaving it here will propagate inconsistent examples and should be corrected in this commit.

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