Add BCE temporal tags to all documents; add temporal-dating steering doc

rulers/qin-shi-huang.md

@@ -4,29 +4,29 @@
 # Qin Shi Huang
 
 ## Overview
-Qin Shi Huang (259–210 BCE) was the first emperor of a unified China, founding the Qin dynasty and establishing centralized imperial governance that would endure for over two millennia.
+Qin Shi Huang (259–210 BCE) was the first emperor of a unified China, founding the Qin dynasty and establishing centralized imperial governance that would endure for over two millennia. @t[259 BCE..210 BCE]
 
 ## Key Facts
-- Born: 259 BCE, State of Zhao
-- Died: 210 BCE (age 49)
-- Reign as emperor: 221–210 BCE
+- Born: 259 BCE, State of Zhao @t[=259 BCE]
+- Died: 210 BCE (age 49) @t[=210 BCE]
+- Reign as emperor: 221–210 BCE @t[221 BCE..210 BCE]
 - Original name: Ying Zheng
 - Dynasty: Qin
 
 ## Achievements
-- Unified the Warring States into a single empire (221 BCE) [^1]
+- Unified the Warring States into a single empire (221 BCE) @t[=221 BCE] [^1]
 - Standardized weights, measures, currency, and writing across China
 - Began construction of the Great Wall by linking existing fortifications
 - Built an extensive road and canal network
 - Terracotta Army: ~8,000 life-sized warrior figures guarding his mausoleum, discovered 1974 [^2]
 
 ## Controversies
-- Burning of books and burying of scholars (~213–212 BCE)
+- Burning of books and burying of scholars (~213–212 BCE) @t[213 BCE..212 BCE]
 - Harsh Legalist governance
 - Massive forced labor for construction projects
 
 ## Legacy
-The Qin dynasty collapsed shortly after his death (206 BCE), but his unification model was adopted by the succeeding Han dynasty.
+The Qin dynasty collapsed shortly after his death (206 BCE), but his unification model was adopted by the succeeding Han dynasty. @t[=206 BCE]
 
 ---
 [^1]: Sima Qian, *Records of the Grand Historian* (*Shiji*)