Add Telegram group chat allowlists and custom triggers

[crankshift]

Summary

• Adds Telegram group chat allowlists, group routing, group settings, ephemeral memory, and group prompt context.
• Adds per-group custom triggers and bounded matching so short triggers do not fire inside longer words.
• Updates public docs, changelog, and release version to 0.7.0.

Commit-derived scope

• feat: add Telegram group chat allowlists
• fix: clarify Telegram DM setup prompt
• fix: use Telegram sender chat authors
• feat: add Telegram group routing
• feat: route/manage/wire Telegram groups by custom triggers
• fix: bound Telegram custom trigger matches
• docs: design, plan, and document Telegram group/custom-trigger behavior

Closes #25

Test Plan

• pnpm run lint
• pnpm test
• pnpm run check