docs: refresh engineering runbooks

[cursor]

Docs added/updated

• Refreshed docs/engineering-guide.md for event-loader contracts, slash-command cooldown caveats, release workflow behavior, and prefix-command requirements.
• Updated setup/config docs in docs/getting-started.md, docs/configuration.md, docs/database.md, and docs/contributing.md for explicit Prisma generation, nodemon availability, MongoDB URI selection, and current test inventory.
• Updated feature/interface docs in docs/features.md, docs/commands.md, docs/architecture.md, and docs/README.md for tickets, Join-to-Create, rank cards, context-menu deployment, and unwired JTC helpers.

Codepaths covered

• src/handlers/events.js and tests/events-handler-shape.test.js
• .github/workflows/release.yml
• package.json scripts
• src/example.config.js, src/events/ready/registerCommands.js, and src/events/ready/registerContextMenus.js
• src/commands/slash/General/rank.js, src/components/modals/ticket-modal.js, src/components/buttons/ticket-close.js, src/components/selects/setupSSM.js, src/events/Guild/jointocreate.js, and prisma/schema.prisma

Key knowledge gaps addressed

• Removed stale warning that Guild { event, run } handlers do not register.
• Corrected release automation from version-diff gating to missing-tag gating.
• Corrected false Prisma postinstall generation guidance and documented nodemon as an external expectation.
• Clarified PRODUCTION=false MongoDB truthiness, DEV_GUILD_ID slash/context registration, required /rank info <user>, ticket transcript recipient/parent-channel behavior, and incomplete JTC setup/user-limit wiring.

Verification

• git diff --check HEAD~1..HEAD
• npm test (37 tests passed)