Refresh engineering documentation runbooks

[cursor]

Summary

• Updated docs/engineering-guide.md to match the current event-loader { event, run } contract and release workflow tag-existence gating.
• Updated docs/configuration.md and docs/getting-started.md for current PRODUCTION/MongoDB URI behavior, DEV_GUILD_ID registration, and explicit Prisma client generation.
• Updated docs/commands.md and docs/features.md so /rank info documents the required user option.

Codepaths covered

• .github/workflows/release.yml
• src/handlers/events.js and tests/events-handler-shape.test.js
• src/events/ready/registerCommands.js and src/events/ready/registerContextMenus.js
• src/example.config.js
• package.json
• src/commands/slash/General/rank.js

Knowledge gaps addressed

• Removed stale release guidance about a HEAD~1..HEAD version-line check.
• Replaced the stale event-loader caveat with the verified current loader contracts.
• Clarified the local-development pitfall where PRODUCTION=false is truthy for MongoDB URI selection.
• Corrected setup docs that implied a Prisma postinstall hook exists.
• Corrected rank docs that described /rank info [user] as optional/defaulting to self.

Validation

• git diff --check
• npm test (37 passing tests)