Use Effect FileSystem in workspace services

[cursor]

What Changed

• Reworked WorkspaceFileSystem.readFile to use Effect FileSystem realpath/open/stat/read APIs instead of node:fs/promises wrapped in Effect.tryPromise.
• Reworked WorkspaceEntries.browse to use Effect FileSystem.readDirectory/stat and structured PlatformError handling for permission-denied directory reads.
• Updated workspace tests to assert structured PlatformError causes and override the file-system service capability instead of mocking node:fs/promises.

Why

These changes make the workspace subsystem more idiomatic Effect: I/O now flows through Effect services, errors stay structured, and tests can override the granular file-system capability without module mocks.

UI Changes

Not applicable; no UI changes.

Checklist

• This PR is small and focused
• I explained what changed and why
• I included before/after screenshots for any UI changes
• I included a video for animation/interaction changes

  

Note

Replace Node.js fs/promises with Effect FileSystem in workspace services

• WorkspaceFileSystem.ts replaces NodeFSP calls with Effect FileSystem for realPath, open, stat, and read in readFile, using Effect.scoped instead of manual acquire/release.
• WorkspaceEntries.ts replaces NodeFSP.readdir with fileSystem.readDirectory + per-entry fileSystem.stat to filter for directories; only PermissionDenied errors return an empty listing — other failures surface as WorkspaceEntriesReadDirectoryError.
• Tests updated to inject a custom FileSystem layer and assert PlatformError causes (e.g. NotFound, PermissionDenied) instead of Node.js ErrnoException codes.
• Behavioral Change: errors from file/directory operations now carry PlatformError as the wrapped cause rather than Node.js errors, changing the error structure visible to callers.

^{Macroscope summarized 40624c1.}

[macroscopeapp]

One Effect convention issue found: use Effect.catchTags rather than Effect.catchTag for handling statically known tagged failures.

^{Posted via Macroscope — Effect Service Conventions}

[macroscopeapp]

Use Effect.catchTags({ ... }) instead of Effect.catchTag for known tagged failures (the convention applies even when handling a single tag). The branch on cause.reason._tag for PermissionDenied remains a valid structural check inside the handler.

Suggested change

	Effect.catchTag("PlatformError", (cause) =>
	cause.reason._tag === "PermissionDenied"
	? Effect.succeed([])
	: Effect.fail(
	new WorkspaceEntriesReadDirectoryError({
	cwd: input.cwd,
	partialPath: input.partialPath,
	parentPath,
	cause,
	}),
	),
	),
	Effect.catchTags({
	PlatformError: (cause) =>
	cause.reason._tag === "PermissionDenied"
	? Effect.succeed([])
	: Effect.fail(
	new WorkspaceEntriesReadDirectoryError({
	cwd: input.cwd,
	partialPath: input.partialPath,
	parentPath,
	cause,
	}),
	),
	}),

^{Posted via Macroscope — Effect Service Conventions}