Improve OPFS sync copy error messages

[akirk]

Motivation for the change, related issues

Persistent Playground sites can fail while copying an OPFS/local-fs mount into
MEMFS during boot. The sync loop previously waited with Promise.any(), so
when all pending copy operations rejected, Firefox surfaced the generic message:

No Promise in Promise.any was resolved

That message hides the entry that failed and the underlying read/write error,
making submitted crash reports hard to diagnose.

Implementation details

• Wrap initial OPFS-to-MEMFS copy failures with the failed MEMFS path and root
  error message.
• Preserve the original error via cause.
• Use Promise.race() while waiting for pending copy operations so the first
  real rejection is surfaced instead of a generic Promise.any() aggregate.
• Add regression coverage for a failed OPFS file read during initial sync.

Example new message:

Failed to copy OPFS entry to MEMFS path "/wordpress/database.sqlite": file could not be read

Testing Instructions

npm exec nx test php-wasm-web -- --runInBand
npm exec nx typecheck php-wasm-web
npm exec nx lint php-wasm-web

Both pass locally.

Note: the test run still prints an existing unrelated Vitest warning from
tcp-over-fetch-websocket.spec.ts about an unawaited assertion.

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Improves diagnosability of OPFS→MEMFS initial sync failures by surfacing the first real underlying copy error (with path context) instead of the generic Promise.any() message, and adds a regression test for failed OPFS reads.

Changes:

• Wrap OPFS-to-MEMFS copy errors with the failing MEMFS path and preserve the original error via cause.
• Switch wait behavior from Promise.any() to Promise.race() to surface the first rejection.
• Add a Vitest regression test covering a failed OPFS file read during initial sync.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
packages/php-wasm/web/src/lib/directory-handle-mount.ts	Improves error wrapping and changes promise waiting strategy to surface real copy failures.
packages/php-wasm/web/src/lib/directory-handle-mount.spec.ts	Adds an in-memory OPFS test harness and a regression test for initial sync error reporting.

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