OpenCode TUI reads input.subagent_type to display task type. When
subagent_type was missing (e.g., category-only or session continuation),
TUI showed 'Unknown Task'.
Fix:
- category provided: always set subagent_type to 'sisyphus-junior'
(previously only when subagent_type was absent)
- session_id continuation: resolve agent from session's first message
- fallback to 'continue' if session has no agent info
Dev removed task-continuation-enforcer entirely. Remove all remaining
references from plugin hooks, event handler, tool-execute-before, and
config schema to align with origin/dev.
