tooling: upgrade pnpm 10 → 11

[goosewobbler]

Move the workspace from pnpm 10 to pnpm 11 (latest major). Currently pinned to pnpm@10.33.0 via the root packageManager field.

Work

• Bump the pin — packageManager in the root package.json → pnpm@11.x (latest stable, with the +sha512… integrity hash from corepack use pnpm@11).
• Regenerate the lockfile — pnpm install to refresh pnpm-lock.yaml (pnpm 11 may bump lockfileVersion / settings); commit the result.
• Standardise CI — workflows currently mix pnpm/action-setup@v4 and @v6. Move everything to @v6 (supports pnpm 11 and resolves the version from packageManager, so no hard-coded version:).
• Review pnpm-workspace.yaml — catalog + settings keys; pnpm 11 changed some config defaults/locations (e.g. settings that moved out of .npmrc / package.json into pnpm-workspace.yaml).
• Check breaking changes — walk the pnpm 11 release notes for default-behaviour changes (hoisting / peer-dependency resolution / node-linker / dangerouslyAllowAllBuilds and the new build-script allowlist). The package-test fixtures (isolated installs) are the most exposed.
• Verify the toolchain — Turborepo + the full build / test / lint / typecheck pipeline on the new pnpm.
• Docs — update AGENTS.md (pnpm 10.27.0+ → 11.x) and any setup docs that name the pnpm version. Optionally add an engines.pnpm pin.

Validation

Clean pnpm install, full build/test/lint/typecheck green, CI green, and the package-test fixtures still resolve their isolated installs.

🤖 Generated with Claude Code