chore: add biome for linting/formatting + CI action for linting in SRC folder

[SheepFromHeaven]

Description

Type of change

• Bug fix
• New feature
• Refactoring / style
• Documentation update / chore
• Other (please describe)

Versioning

• Version is updated
• Changed files hash is updated

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[SheepFromHeaven]

this should be a good one early on in our refactor. To keep consistent styling. I chose biome for speed reasons.

[Copilot]

Pull request overview

This PR introduces Biome as the formatter/linter for the TypeScript sources and wires it into both local tooling and CI, while applying Biome-driven formatting and a few small safety/consistency tweaks across the src tree. It also adds an initial unit test for stringUtils.round.

Changes:

• Added Biome configuration (biome.json), npm scripts (lint, format), and a GitHub Actions workflow to enforce linting on pushes and PRs.
• Reformatted and lightly refactored multiple utilities and modules in src/ to satisfy Biome rules (e.g., parseInt radix, Number.isNaN, stronger typing, safer optional handling).
• Introduced a Vitest unit test for round in stringUtils, exercising behavior with undefined input.

Reviewed changes

Copilot reviewed 29 out of 30 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/utils/unitUtils.ts	Refactored temperature and SI helpers to use template strings and explicit parseInt radix for Biome compliance.
src/utils/stringUtils.ts	Reformatted helpers, adjusted regex style, and suppressed unused error variables in JSON helpers; core behavior otherwise unchanged.
src/utils/stringUtils.test.ts	Added a Vitest test asserting round(undefined) returns an empty string (currently not satisfied by implementation; see inline comment).
src/utils/probabilityUtils.ts	Reordered imports, reformatted functions, used Number.isNaN and exponent operator, and expanded gauss for clarity.
src/utils/polyfills.ts	Reflowed polyfill implementations and typings for replaceAll, flat, and async iterator on ReadableStream without altering behavior.
src/utils/pathUtils.ts	Reformatted path/isolines utilities, improved typed options, and made internal closures more explicit while preserving existing logic.
src/utils/numberUtils.ts	Switched Math.pow to exponent operator and added semicolons; numeric behavior remains the same.
src/utils/nodeUtils.ts	Converted helper functions to arrow functions and tightened parent typing without changing semantics.
src/utils/languageUtils.ts	Replaced new RegExp with regex literals, made heavy use of template strings, and slightly clarified getAdjective implementation.
src/utils/index.ts	Reordered imports and window augmentations for consistency, and wrapped several window-exposed bindings for clarity while keeping the global API stable.
src/utils/graphUtils.ts	Reorganized imports, strengthened typings (Cells, Vertices, Point), and refactored several helpers (Voronoi grid, quadtree search, height drawing) for readability and safer numeric handling.
src/utils/functionUtils.ts	Reformatted rollups and distanceSquared and clarified internal nest helper signature.
src/utils/debugUtils.ts	Reordered imports, expanded drawing helpers (drawPoint, drawPath) and ensured window typings reflect debug helpers.
src/utils/commonUtils.ts	Reformatted utility helpers, added safer setTimeout usage, enforced parseInt radix, and slightly clarified prompt initialization logic.
src/utils/colorUtils.ts	Split d3 imports, added type annotations, and refactored color helpers to use template strings and explicit HEX formatting.
src/utils/arrayUtils.ts	Clarified deep-copy helper internals, made cf map typing more generic, and improved typed-array factory assertion messaging.
src/types/global.ts	Normalized imports to double quotes and converted PackedGraph import to a type-only import.
src/types/PackedGraph.ts	Reformatted TypedArray union across multiple lines and kept PackedGraph layout intact.
src/modules/voronoi.ts	Switched Delaunator import to type-only, restructured Voronoi fields and methods formatting, and slightly clarified some math operations.
src/modules/river-generator.ts	Reorganized imports, reformatted class methods, improved naming/spacing in river generation logic, and made some numeric expressions clearer.
src/modules/ocean-layers.ts	Simplified imports, reordered parameters, and made vertex connection logic and path generation more readable.
src/modules/lakes.ts	Reordered imports, converted PackedGraphFeature to a type import, and clarified lake climate calculations and cleanup logic.
src/modules/index.ts	Ensured module side-effect imports include ./biomes with a trailing semicolon to keep module initialization order consistent.
src/modules/heightmap-generator.ts	Renamed class to HeightmapModule, updated the global type, and significantly reformatted heightmap generation while preserving algorithmic behavior.
src/modules/features.ts	Reorganized imports from ../utils, refactored feature-markup helpers for clarity, and made use of clipPoly and connectVertices more explicit.
src/modules/biomes.ts	Reformatted biome configuration data, clarified arrays (names, colors, costs), and expanded define and getId signatures.
package.json	Added @biomejs/biome devDependency and lint/format scripts invoking Biome.
package-lock.json	Locked @biomejs/biome and its platform-specific binary packages, and updated dependency metadata accordingly.
biome.json	New Biome configuration enabling formatter and linter for src/**/*.ts, with customized rules (including useParseIntRadix and noUnusedVariables).
.github/workflows/lint.yml	New GitHub Actions workflow running biome ci . on push and PR to enforce linting/formatting in CI.

[SheepFromHeaven]

ready for merge