Add verification nudges to workflow tasks

[shouc]

Summary

• add Claude-style verification nudges to TodoWrite and TaskUpdate when a 3+ item list is fully closed without any verification step
• keep the reminder logic in the bounded workflow runtime instead of touching the larger prompt-parity branches already open
• add workflow execution tests for the nudge and team-context suppression paths

Scope exclusions

• left PR Restore full Claude-compatible tool prompts for OpenAI #20 tool-prompt parity work untouched
• left PRs Restore Claude-compatible /compact local command flow #21-Implement mcp reset-project-choices #26 untouched

Verification

• cargo test -p puffer-core tool_execution::workflow -- --nocapture
• cargo test -p puffer-core agent_runtime -- --nocapture