feat(agentic): add configurable AI agent role/persona system (Harvester, Curator, Reviewer, Fixer, Delegator)

[jbdevprimary]

Summary

PR #41 (closed as superseded — its diff targeted the pre-restructure agentic-control package) proposed a generic roles module for @jbcom/agentic with configurable AI agent personas. Sage (Q&A, task decomposition, agent routing) has since been delivered via a different path — it's implemented in packages/triage/src/{tools,schemas,handlers,cli}/sage.ts (see #40, closed as satisfied).

The remaining five personas from #41's design were never implemented and represent real, still-wanted scope:

Role	Purpose	Trigger
Harvester	PR lifecycle, review management, merging	Schedule (15min)
Curator	Nightly triage, issue assessment, agent spawning	Schedule (2am)
Reviewer	AI code review	PR events, /review
Fixer	CI failure resolution	CI failure events
Delegator	Issue → agent routing	/cursor, /jules

Proposed design (from #41, adapted to the current package layout)

• packages/agentic/src/roles/types.ts — RoleDefinition, RoleConfig, RoleTrigger, AgentCapability
• packages/agentic/src/roles/defaults.ts — default definitions for the five roles above
• packages/agentic/src/roles/executor.ts — executeRole, listRoles, findRoleByTrigger, getEffectiveRole
• agentic roles CLI subcommands: list, info <role>, match <trigger>
• AgenticConfig.roles config surface (per-role enabled/model overrides)

Notes for implementer

• Should compose with the existing fleet/handoff/triage primitives in packages/agentic and packages/triage rather than duplicating them — Harvester/Reviewer/Fixer/Delegator overlap conceptually with packages/agentic/src/triage/pr-triage-agent.ts and packages/agentic/src/handoff/manager.ts; check for consolidation opportunities before adding new code paths.
• feat(roles): Add configurable AI agent personas (Sage, Harvester, Curator, etc.) #41's original test plan left integration tests unchecked — write those as part of this work, not as a follow-up.