Modernize Javascript and tool chain

[sderrow]

Why

The upstream bottleneck library is no longer maintained, and its CoffeeScript source + ES5-targeted toolchain are increasingly out of step with the modern Node.js ecosystem. This PR rewrites the codebase and tooling so the fork can be a long-lived, easier-to-contribute-to home for further work (eventually a native TypeScript port).

What changes

This is a large diff but most of it is mechanical (CoffeeScript → JS, test renames, toolchain swaps). The runtime behavior is unchanged — same scheduling/limiting semantics, same job lifecycle, same events. The API surface does change in a few intentional v4 ways (see Breaking changes below), mostly around how Redis clients are wired in and the removal of the ES5 build.

Source modernization

• Converted all CoffeeScript sources under src/ to modern JS via decaffeinate, then committed the JS as the source of truth (CoffeeScript is removed from the repo and the build).
• Reorganized Redis-only code under src/cluster/ (datastore, connections, Lua scripts, Scripts.js) so the local-only "light" build no longer needs to know about Redis. Public exports are unchanged.
• Dropped support for the legacy redis v2/v3 client API; cluster mode now requires redis v4+ (and works with v5) or ioredis v5+.
• Made ioredis and redis optional peer dependencies — the library no longer implicitly require()s a Redis client; consumers bring their own and pass a Redis constructor (or pre-built client/connection).

Toolchain

• Migrated the build/package manager from npm + Babel + Rollup to pnpm + tsdown.
• Added lint/format with oxc (oxlint, oxfmt) — the project previously had no lint or format tooling.
• Replaced the legacy es5.js / light.js Rollup configs with a single tsdown.config.ts. The ES5 build is removed; the UMD @sderrow/bottleneck/light build remains for browser/non-Node consumers.
• Added tsconfig.json, .oxlintrc.json, .oxfmtrc.json, .nvmrc, and a Husky + lint-staged pre-commit hook.
• Replaced Travis with a GitHub Actions CI workflow (.github/workflows/ci.yaml) plus a reusable setup composite action.

Tests

• Migrated the suite from Mocha-style files to Vitest with vitest.config.ts defining separate projects (local, ioredis, node-redis, light-smoke, memory).
• Renamed test files to the *.test.js convention and split the monolithic cluster.js / general.js into focused files (cluster.test.js, cluster-coordination.test.js, general.test.js, general-traffic.test.js, etc.).
• Extracted shared test scaffolding into test/helpers/ (limiter setup, call logging, job tracking, state waiting) and added Testcontainers-based Redis fixtures (global-setup-redis.ts) so cluster tests no longer depend on a manually-run Redis instance.
• Added smoke and memory-leak suites under test/smoke/ and test/memory/.

Packaging

• Bumped to 4.0.0-rc.0 and renamed the package to @sderrow/bottleneck.
• New exports map exposes . and ./light with shared bottleneck.d.ts types; dist/ is the published build output.

Breaking changes (v4)

• require("bottleneck/es5") is gone — use @sderrow/bottleneck/light if you need a UMD build.
• Cluster mode requires redis v4+ or ioredis v5+.
• ioredis / redis must be installed by the consumer (peer deps).
• The Redis constructor option is required when datastore is "redis" / "ioredis" unless you pass a pre-built client or connection.
• Internal Redis modules moved to src/cluster/ (only matters if you imported from internal paths).

Follow-ups (out of scope)

• Native TypeScript rewrite of src/.

[sderrow]

• Modernize Javascript and tool chain #5 👈 (View in Graphite)
• Update package.json and readme #6
• master

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