Support linked npm workflows with persistent WASI symlinks

[noise64]

• resolves GOL-388
• replaces runtime-local symlink placeholders with persistent relative WASI filesystem symlinks shared across fresh execution runtimes
• enables local npm exec, npx, workspace links, npm link, registry-acquired bins, and representative pnpm-style package layouts
• preserves the invoked .bin symlink path in process.argv[1], matching Node.js 22.14, while realpath-based module identity remains unchanged
• rejects rooted symlink targets atomically with EINVAL; WASI preview 2 cannot resolve those targets inside a preopen
• adds P2/P3 filesystem, execution, npm workflow, module identity, broken-link, cycle, rename, unlink, and exact-argv coverage
• stacked on Run npm package-management workflows inside wasm-rquickjs #125; rebase onto main after that PR merges
• TODO: GOL-427 tracks Windows linked workflows without Developer Mode or equivalent symlink privilege

Node compatibility

• primary CI-enforced: 3215/4387 (73.3%) → 3174/4387 (72.4%)
• full public: 3215/5750 (55.9%) → 3174/5750 (55.2%)
• fs: 373 passing / 12 gaps → 339 passing / 46 gaps
• module: 129 passing / 25 gaps → 122 passing / 32 gaps
• the 41-test decrease is an intentional, honest reclassification: those vendored tests require rooted symlink targets that WASI cannot provide; persistent relative-link behavior is covered by focused runtime tests

Performance

• warmed cloud_sdk_offline: 29.011 s on Run npm package-management workflows inside wasm-rquickjs #125 → 25.666 s on this branch; no measured regression from persistent symlink handling