Sprint 3.3: Introduce Trust/Threat axes for faction diplomacy

[Copilot]

Currently the diplomacy system tracks only a single standing value per faction. This PR introduces independent trust_level and threat_level axes (as specified in COMBAT_SYSTEM_DESIGN §6.1), wires them into trade/agreement/war mechanics, and surfaces both values in the UI.

DB

sql/migrate_trust_threat_v1.sql — adds to diplomacy:

• trust_level DECIMAL(5,2) (0–100) — bilateral trust built via cooperation
• threat_level DECIMAL(5,2) (0–100) — threat perception from aggression/fleet
• trust_decay_rate DECIMAL(4,3) — hourly decay rate (default 0.5)

Seeds initial values from existing standing (positive standing → trust, negative → threat).

API

api/faction_relations.php

• standing action now returns trust_level + threat_level per faction
• New GET ?action=trust_threat — per-faction trust/threat + derived stance
• New POST ?action=update_trust_threat — write trust/threat deltas with clamping
• _diplo_stance(trust, threat) helper: ALLY | FRIENDLY | NEUTRAL | TENSE | HOSTILE

api/diplomacy.php

• fa_ai_acceptance() now factors trust (+15 max) and threat (−20 max) into NPC acceptance probability
• Alliance proposals blocked when threat_level ≥ 75
• Accepted agreements award type-specific trust gains (trade +5, research +8, alliance +10, non_aggression +3)
• Cancellations apply trust penalties (−5 default, −15 for alliance)

api/factions.php

• trade_offers applies a threat surcharge: every 10 threat points above 50 reduces effective standing by 1, narrowing the visible offer pool

UI

RuntimeDiplomacyDataModel.js — new pure helpers:

dm.trustMeta(60)              // { cls: 'trust-moderate', label: 'Moderate Trust' }
dm.threatMeta(80)             // { cls: 'threat-critical', label: 'Critical Threat' }
dm.diploStance(80, 10)        // { code: 'ALLY', label: 'Ally', cls: 'stance-ally' }
dm.trustThreatBarsHTML(65, 20) // dual progress bars + stance chip HTML

RuntimeDiplomacyPanel.js — trust/threat bars rendered in faction panel header alongside agreements.

RuntimeFactionsController.js — each faction card gains 🤝 N / ⚠️ N badges and a derived stance chip; syncFactionCard() keeps them live on standing updates.

Tests

18 new tests in diplomacy-panel.test.js covering all trust/threat helpers (trustMeta, threatMeta, diploStance, trustThreatBarsHTML) and panel rendering with trust/threat data (40 tests total).