Addresses confusion between interrupt, stop, kill, and delete operations
in the ambient workflow guidance.

Changes:
- protocol.md: Added "Agent Lifecycle Operations" section with clear
  definitions and distinctions between each operation
- mcp_tools.go: Updated stop_agent, spawn_agent, and restart_agent tool
  descriptions to clarify behavior and data preservation
- api-reference.md: Added lifecycle operations summary and expanded
  endpoint descriptions to clarify what is preserved vs deleted
- AgentDetail.vue: Updated tooltips and dialog text to reinforce that
  kill/stop/restart preserve agent records while delete removes all data

Key clarifications:
- Interrupt = pause current task (agent keeps running)
- Stop/Kill = end session cleanly (preserves agent record, can restart)
- Delete = permanent removal (all data deleted, cannot restart)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Resolved conflict in AgentDetail.vue by accepting main's dropdown menu
approach for lifecycle actions. This supersedes the flex-wrap grouping
from PR jsell-rh#288 while preserving all flex-wrap additions on other rows.

Main's dropdown menu is a better UX solution for mobile/overflow issues
and already includes all flex-wrap improvements from frontend-ui.

Changes merged from main:
- AgentDetail.vue: Dropdown menu for lifecycle actions
- AgentMessages.vue: Session active warning and input disabling