chore: add AGENTS.md and Cursor rules for AI-assisted development

[MaartenUreel]

Torn username and ID: Murfy [420016]

• Read CONTRIBUTING.md.
• Added your name in src/common/utils/team.ts file.
• Update the unreleased version of src/extension/assets/changelog.json file
• Bump the versions of all related userscripts (n/a - no feature code changed)

Is this PR:

• for a new feature ?
• an issue fix ?
• a developer QoL PR ?

Purpose of PR:

The repo had no machine-readable conventions, so every AI coding agent re-derived them from scratch and got the
wiring wrong. This adds AGENTS.md plus seven glob-scoped Cursor rules that document what the code already does.

AGENTS.md is deliberately short since it loads on every request: Bun-only toolchain, repo layout, path aliases,
code style, the PR gates, and the cross-cutting requirements (changelog entry, userscript version bumps, docs page).

The rules under .cursor/rules/ attach only when the relevant files are touched:

Rule	Covers
torntools-features	The Feature contract, lifecycle order, manual registration in script-manager.ts, the fact there is no cleanup hook
torntools-userscripts	Entry metadata, context tiers, and that a shared feature change requires a metadata.ts version bump to publish
torntools-svelte-ui	Svelte 5 runes, ui/ being vendored shadcn, and the four files a new setting touches
torntools-torn-page-dom	findElement over querySelector, requireElement over polling, containers/filters, Torn's hashed class names
torntools-data-storage-api	ttStorage vs the sync globals, DefaultSetting, relay: true, apiUsage gating, migrations, opt-in external services
torntools-extension-shell	WXT entrypoint naming, the --inject main-world pattern, background proxy services
torntools-docs	The __placeholder.mdx template and its mandatory sections

Also adds a verify script (lint && types && types:svelte && test) so contributors have one command matching the
PR gates, and *.mdc text eol=lf in .gitattributes for consistency with the existing *.md rule.

No runtime code is touched.

Linked issues:
None