id-chaining: emit hf_id across narrative tools (P0)

[alexanderolvera]

historical_figure(hf_id) is useless without a discoverable input. Today none of the narrative tools emit one.

• site_history.notable_deaths[] and battles[] emit slayer / general / victim names only — no ids to chain on.
• citizen relations drop unit_id exactly when the figure is dead — which is precisely the case narrative cares about (a dead father, a lost spouse).
• chronicle speakers carry a unit id but no hf id.

Add hf_id to each. Small and mechanical, but it is the hinge the legends read hangs on.