feat: configure llmdoc startup context

[Disdjj]

Summary

• add llmdoc.config/v1 with configurable SessionStart skill reminders and ordered cold-start document preload
• keep cold-start preload unbudgeted with a completion marker, while compact re-entry lists document IDs without reinjecting full bodies
• preserve valid remindSkill choices across preload errors, deduplicate normalized aliases with warnings, and synchronize preload references through mv/prune workflows
• publish the config schema at https://llmdoc.tokenroll.ai/schemas/config.schema.json and verify it in website CI
• make fixed CLI, hook, JSON-message, and Viewer interface text English while preserving Chinese search and document content
• add dogfood config, startup-config skill guidance, generated-surface parity checks, and llmdoc knowledge updates
• bump package and plugin surfaces to 3.6.0

Validation

• npm run typecheck
• npm run lint
• npm test (70 passed)
• npm run check:prompts
• node scripts/check-codex-surface.mjs
• npm run validate:dogfood
• website: npm run check, npm run build, npm run check:schema