Add GraphSignedConflictAdvisor: agentic signed-graph conflict-mediation advisor

Sibling to GraphAdversaryForecaster, GraphPrivacyExposureAuditor,
GraphInfluenceSeedAdvisor, GraphCascadingFailureAdvisor,
GraphCommunityChurnAdvisor, GraphIntelligenceAdvisor.

Consumes a signed graph (via SignedGraphAnalyzer: triangle census,
structural balance, frustration index, coalitions) and produces a
P0-P3 conflict-mediation playbook with an A-F portfolio grade.

- Per-vertex verdicts: PEACEMAKER / NEUTRAL / POLARIZED / AGITATOR /
  ISOLATED_HOSTILE / BROKER.
- Per-edge verdicts on frustrated edges: FLIP_CANDIDATE /
  CUT_CANDIDATE / MEDIATE_CANDIDATE.
- Playbook actions: ISOLATE_AGITATORS (P0), EMERGENCY_DE_ESCALATION
  (P0), SPLIT_HOSTILE_CLIQUE (P1), FLIP_EDGE_TO_POSITIVE (P1),
  ELEVATE_BROKERS (P1), PAIR_PEACEMAKERS_WITH_POLARIZED (P1),
  MONITOR_COALITION_DRIFT (P2), SCHEDULE_DIALOGUE_SESSION (P2),
  HEALTHY_NETWORK (P3 fallback).
- RiskAppetite (CAUTIOUS/BALANCED/AGGRESSIVE) modulates conflict
  scores and playbook trimming.
- Deterministic given a fixed Clock; byte-stable JSON renderer.
- Text, Markdown, and JSON renderers.
- Pure JDK + JUNG. Never mutates the input graph.

Includes 15 JUnit 4 tests covering empty/trivial graphs, balanced
triangles, frustrated triangles, hostile stars, agitator detection,
risk-appetite monotonicity, AGGRESSIVE P3 trimming, CAUTIOUS dialogue
scheduling, JSON byte-stability, markdown sections, render headline,
input-graph immutability, topK capping, and coalition detection.

Author: sauravbhattacharya001