feat: replace external sample documents with bundled demo content (#956)

Replaces the URL-based PDF downloads in tg-load-sample-documents with
seven curated, locally bundled documents covering diverse topics (recipes,
Belgian beer, trade routes, corporate scandals, pets, fortifications,
Bronze Age collapse). Documents are packaged as data files within
trustgraph-cli and loaded from metadata.json, removing the dependency
on external URLs and the doc-cache mechanism.

test-data/history-of-pets.md

@@ -0,0 +1,13 @@
+# The Domestic Canopy: A Unified Narrative of Companionship
+
+The story of the human-animal bond begins not with a conscious decision to breed a companion, but with an ancient, mutual opportunism in the frozen wastes of the late Pleistocene. Long before the advent of agriculture, the gray wolf (*Canis lupus*) began to separate from its wild packs, drawn to the peripheral campfires of Eurasian hunter-gatherers. These ancestral canids, which would morph over millennia into the domesticated dog (*Canis lupus familiaris*), offered early humans an unparalleled early-warning system against apex predators and an invaluable partner in the persistence hunt. In return, humans provided a steady supply of megafauna marrow, cooked gristle, and proximity to warmth. This biological pact was so profound that it transcended mere utility, as evidenced by the late Paleolithic Natufian burial sites in the Levant, where human skeletons were interred with their hands resting gently upon the ribcages of wolf pups, marking the earliest archaeological signature of the transition from working tool to sentimental proxy.
+
+As the ice sheets retreated and humanity anchored itself to the soil during the Neolithic Revolution, the nature of animal companionship shifted dramatically, giving rise to an entirely different ecological dynamic in the Fertile Crescent. The rise of grain storehouses in ancient Egypt attracted unprecedented swarms of rodents, creating a pristine ecological niche for the North African wildcat (*Felis lybica*). Unlike the highly structured social hierarchy of the wolf, the cat domesticated itself on terms of aloof independence, transitioning from a tolerated pest-control mechanism to a revered icon of divine protection. By the time of the Egyptian Middle Kingdom, cats were so thoroughly integrated into the domestic fabric that they were granted formal mourning rites; Roman historians like Herodotus noted that when a house cat died of natural causes, the entire human household would shave their eyebrows as a public manifestation of grief. These felines were often mummified using the same costly natron resins reserved for the nobility and entombed in specialized necropolises like Bubastis, dedicated to the feline-headed deity Bastet, effectively blending religious cosmology with domestic affection.
+
+Parallel developments were unfolding across the globe, creating distinct regional pockets of companionship that would later collide through imperial trade. In the Andean highlands of South America, the Incas domesticated the guinea pig (*Cavia porcellus*), known locally as the cuy. While primarily a source of protein and a diagnostic tool used by folk healers to absorb illness from the sick, select lineages were kept by children as cherished house-dwellers. Meanwhile, in the imperial courts of Han Dynasty China, a parallel phenomenon saw the intensive breeding of the Pekingese dog. These small, flat-faced canids were selectively bred to resemble miniature lions — the mythical protectors of Buddhism — and were guarded so fiercely within the walls of the Forbidden City that stealing one was punishable by death. They lived a life of pampered luxury, carried in the sleeves of silk robes and tended to by dedicated eunuchs, establishing an early historical precedent where certain animal breeds functioned strictly as status symbols and manifestations of political sovereignty rather than utilitarian workers.
+
+The classical antiquity of Europe further complicated this tapestry, as the Roman elite integrated exoticism into their definition of the domestic sphere. Roman matrons frequently kept ring-necked parakeets (*Psittacula krameri*) imported from the conquests of India, housing them in elaborate cages of ivory and silver, and teaching them to speak the name of the Emperor. Concurrently, the Roman fondness for the ferret (*Mustela furo*) emerged as a dual-purpose phenomenon; these mustelids were kept both to flush rabbits from agricultural burrows and as slinky, playful companions within the villa. This Roman domestic ecosystem was heavily documented by Pliny the Elder in his Natural History, where he noted that the elite often developed deep, seemingly irrational emotional attachments to their companion animals, including pet fish like the moray eel, which the orator Hortensius reportedly wept over when it died in his private ornamental pond.
+
+The medieval period in Europe introduced a sharp class divide to the concept of the pet, often viewed through the suspicious lens of ecclesiastical authority. While the peasantry kept functional yard dogs and barn cats, the high nobility — particularly noblewomen and monastic figures — indulged in the keeping of lapdogs, such as the early Maltese, and refined birds of prey. These lapdogs were often criticized by conservative church theologians who argued that the excessive meat fed to pampered pets belonged in the mouths of the starving peasantry. Furthermore, during the height of the European witch trials, the domestic pet — particularly the black cat, the toad, or the ferret — was frequently demonized by inquisitors as a "familiar," a physical vessel housing a demonic spirit. This created a perilous cultural paradox where an animal could be viewed as a comforting hearth-companion in one household and an existential piece of heretical evidence in another.
+
+The modern concept of pet-keeping as a universal consumer phenomenon crystallized during the Industrial Revolution and the rise of the Victorian middle class. As populations migrated from rural farms to dense urban centers, the severed connection to nature triggered a romanticized counter-movement. The Victorians elevated the domestic home into a moral sanctuary, and the pet was introduced as a pedagogical tool to teach children empathy, kindness, and middle-class domestic virtues. This era saw the birth of the commercial pet industry: standard kibble formulations were patented by James Spratt in the 1860s, dog shows like Crufts were established to formalize breed standards, and specialized pet cemeteries, like the one in London's Hyde Park, emerged to afford animals a dignified transition into the afterlife. The pet was no longer a working asset or an eccentric luxury of the aristocratic elite; it had become an institutionalized member of the nuclear family unit, setting the stage for the hyper-commodified, emotionally complex multi-billion dollar pet industry of the contemporary era.