docs: relocate frontend docs for agents and human (#31714)

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

web/docs/lint.md

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+# Lint Guide
+
+We use ESLint and Typescript to maintain code quality and consistency across the project.
+
+## ESLint
+
+### Common Flags
+
+**File/folder targeting**: Append paths to lint specific files or directories.
+
+```sh
+pnpm eslint [options] file.js [file.js] [dir]
+```
+
+**`--cache`**: Caches lint results for faster subsequent runs. Keep this enabled by default; only disable when you encounter unexpected lint results.
+
+**`--concurrency`**: Enables multi-threaded linting. Use `--concurrency=auto` or experiment with specific numbers to find the optimal setting for your machine. Keep this enabled when linting multiple files.
+
+- [ESLint multi-thread linting blog post](https://eslint.org/blog/2025/08/multithread-linting/)
+
+**`--fix`**: Automatically fixes auto-fixable rule violations. Always review the diff before committing to ensure no unintended changes.
+
+**`--quiet`**: Suppresses warnings and only shows errors. Useful when you want to reduce noise from existing issues.
+
+**`--suppress-all`**: Temporarily suppresses error-level violations and records them, allowing CI to pass. Treat this as an escape hatch—fix these errors when time permits.
+
+**`--prune-suppressions`**: Removes outdated suppressions after you've fixed the underlying errors.
+
+- [ESLint bulk suppressions blog post](https://eslint.org/blog/2025/04/introducing-bulk-suppressions/)
+
+### Type-Aware Linting
+
+Some ESLint rules require type information, such as [no-leaked-conditional-rendering](https://www.eslint-react.xyz/docs/rules/no-leaked-conditional-rendering). However, [typed linting via typescript-eslint](https://typescript-eslint.io/getting-started/typed-linting) is too slow for practical use, so we use [TSSLint](https://github.com/johnsoncodehk/tsslint) instead.
+
+```sh
+pnpm lint:tss
+```
+
+This command lints the entire project and is intended for final verification before committing or pushing changes.
+
+## Type Check
+
+You should be able to see suggestions from TypeScript in your editor for all open files.
+
+However, it can be useful to run the TypeScript 7 command-line (tsgo) to type check all files:
+
+```sh
+pnpm type-check:tsgo
+```
+
+Prefer using `tsgo` for type checking as it is significantly faster than the standard TypeScript compiler. Only fall back to `pnpm type-check` (which uses `tsc`) if you encounter unexpected results.