* Add /helper thread moderation commands with webhook tracking
- add new /helper root command with guild-only subcommands: warn-new-thread and close-thread
- implement warn-new-thread optional user mention support (matching prior /say new-thread mention behavior)
- implement close-thread thread-only guard, then post close message and archive/lock thread
- remove /say new-thread subcommand and route this workflow to /helper
- add shared command webhook utility posting to HELPER_COMMAND_WEBHOOK_URL
- include webhook payload fields: threadId, messageCount, time, command, invokedBy
- wire helper command registration in src/index.ts and extend env typings
- document HELPER_COMMAND_WEBHOOK_URL and helper command usage in README/.env.example
- fix TS typing issues uncovered during validation: interaction.user nullability, thread type guard, github option literal types
Validation: npx tsc --noEmit passes
* Add shared secret header for helper webhook delivery
- read HELPER_COMMAND_WEBHOOK_SECRET from env
- include x-helper-webhook-secret header on helper webhook POST when configured
- document new env var in README and .env.example
- extend ProcessEnv typing with HELPER_COMMAND_WEBHOOK_SECRET
* Add helper-thread welcome message on thread creation
- add ThreadCreate listener to post onboarding guidance for new helper threads
- target one configured helper parent channel via HELPER_THREAD_WELCOME_PARENT_ID
- set default in-file helper welcome template (overrideable via HELPER_THREAD_WELCOME_TEMPLATE)
- register listener in src/index.ts and update env/docs typing and examples
* Add /helper close command for thread lock+archive
- add /helper close subcommand that posts close message then archives and locks thread
- keep /helper close-thread as compatibility alias using shared close flow
- update README command list
* Updated to mention Krill by ID and compact welcome message
* Add moderated Answer Overflow solution marking
* Send worker event for welcome threads
* Add Hermit-managed thread length monitoring
* Migrate helper logs into Hermit
* Improve Hermit README
* fix: harden thread monitoring and helper log limits
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Co-authored-by: Shadow <hi@shadowing.dev>
