feat(workspace): add concurrency option and --concurrency CLI flag

[jpzwarte]

• This PR contains AI-generated code, but I have carefully reviewed it myself. Otherwise, my PR may be closed.

Description

Large workspaces can spawn an excessive number of subprocesses (e.g. TypeScript declaration workers) when all packages build at once, exhausting system resources (#929).

Add workspace.concurrency to limit how many packages build in parallel, with a --concurrency <count> CLI alias. All formats of a package share one concurrency slot, since a package's exports/publint step only resolves once every format of that package has finished. Defaults to unlimited, preserving current behavior.

Linked Issues

Fixes #929

Additional context

Claude generated the Chinese documentation. Please review that yourself as i can't read Chinese :)

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commit: 6b58931

[jpzwarte]

@sxzz I've tried to make sure this PR follows your earlier comment in the other PR i just closed. Afaics it's ready for review. Please let me know if there's anything i missed.

[Copilot]

Pull request overview

Adds a workspace-level concurrency limit to reduce resource exhaustion in large monorepos by throttling how many workspace packages are built in parallel, surfaced as both workspace.concurrency and a --concurrency <count> CLI flag.

Changes:

• Introduces workspace.concurrency (and --concurrency) and threads the resolved concurrency value through config resolution into the build scheduler.
• Updates the build scheduler to limit parallelism at the package level (all formats for a package share one concurrency slot).
• Adds a mapConcurrent utility with unit tests, plus an e2e fixture/snapshot covering the new option wiring.

Reviewed changes

Copilot reviewed 12 out of 13 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
tests/e2e.test.ts	Adds an e2e scenario that uses workspace.concurrency.
tests/snapshots/workspace-concurrency-option.snap.md	Snapshot output for the new e2e scenario.
src/utils/general.ts	Adds mapConcurrent helper to run async tasks with a concurrency cap.
src/utils/general.test.ts	Unit tests for mapConcurrent (order, cap, rejection, unlimited).
src/config/workspace.ts	Validates/derives workspace.concurrency and returns it from workspace resolution.
src/config/types.ts	Documents Workspace.concurrency and adds InlineConfig.concurrency (CLI alias).
src/config/index.ts	Aggregates workspace concurrency and returns it from resolveConfig().
src/cli.ts	Adds --concurrency <count> flag.
src/build.ts	Applies concurrency when building workspace packages by grouping configs per package.
docs/zh-CN/reference/cli.md	Documents --concurrency <count> in Chinese CLI reference.
docs/reference/cli.md	Documents --concurrency <count> in English CLI reference.

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[jpzwarte]

@sxzz I'm not sure what is happening with the 2 failing checks (autofix and linting). When i run linting locally i get no errors and the errors on GitHub point to lines that i haven't touched in this PR...

[sxzz]

Thank you for your contribution and for helping move this forward! I ended up implementing the feature directly on main with a different design: the concurrency limit is CLI-only and applies to each Rolldown build. I added you as a co-author of commit 8a14c35 to acknowledge your work and contribution. Thanks again!