Improve starter gameplay and bot population lifecycle

[pmbstyle]

Summary

This PR improves the early-game loop and makes the simulated population grow like a persistent world rather than a static bot pack.

Player-facing gameplay

• Gatekeepers now present quest and teleport actions together when both are available.
• City shot merchants stock Soulshots, Spiritshots, and Blessed Spiritshots at the town's intended grade only: no-grade in starter villages; D in Gludin, Gludio, and Dion; C in Giran; B in Oren, Hunter's Village, and Heine; A in Aden; and S in Goddard and Rune.
• Static stalls in the starter villages, Oren, Hunter's Village, and Aden use geodata-validated ground positions near each town's gatekeeper, so their stores remain visible and selectable.
• Respawned NPCs clear stale known-object state, so a monster that has respawned can be targeted and attacked immediately.

Persistent bot population

• Replaced the legacy static adventurer spawn with racial starter cohorts: 30 Human, Elf, Dark Elf, Orc, and Dwarf bots on the level-one starter grounds.
• Expanded the population in paced cohorts while retaining regional balance and same-race starter-party grouping.
• The hard cap covers every generated bot, including characters temporarily running a private store; fixed merchant and crafting service stations remain outside that cap.
• At x1-x10, a new cohort opens once the previous cohort averages level 5. At x50 and higher, it waits for level 10 to avoid flooding starter areas on fast rates.
• Removed level-based automatic gear grants. Bots now evaluate gear needs, earn Adena, buy reasonable equipment, or farm drops before continuing their progression.
• Generated bots do not trade before level 10. Loot from level 1-5 mobs is retained instead of becoming immediate market or NPC-liquidation stock, while crafting materials remain sellable once trading begins.
• No-grade private stores use the nearest racial starter market to their farming location instead of falling back to Giran.

Reliability and observability

• Added source-mob-level provenance to background drops for the sale policy.
• Added generated bot names that remain client-safe and varied.
• Added coverage for staged population limits, race/region seeding, starter party grouping, high-rate wave pacing, market eligibility, low-level loot protection, gear acquisition, gatekeeper menus, merchant shop stock, and NPC visibility after respawn.

Validation

• npm run check
• git diff --check
• node tests/test_population_seed_planner.js
• node tests/test_bot_cold_market_listing.js
• node tests/test_bot_background_drops.js
• node tests/test_bot_gear_acquisition.js
• node tests/test_gatekeeper_teleports.js
• node tests/test_npc_known_object_lifecycle.js
• node tests/test_npc_shop_stock.js
• node tests/test_bot_market_town_routing.js

Live verification

On a fresh x50 bot wipe, the server seeded 150 level-one adventurers evenly across the five racial starter regions, kept pre-10 bots out of trade, formed race-local starter parties, and deferred the second cohort until the level-10 threshold.