fix(core): FileSystem boot realPath probes the server fs for workspace Locations

What

The Location `FileSystem` service resolves `location.directory` with a process-local `realPath` during Location boot (`packages/core/src/filesystem.ts:66`). For a workspace-backed Location whose directory exists only inside the sandbox, boot fails or resolves against the wrong host, so the Location cannot fully construct on a server without a matching local directory.

Fix direction

For `location.workspaceID` placements, skip host realpath canonicalization (treat the configured directory as canonical) or defer canonicalization to first execution-plane use via `Environment.files`. Must not trigger provisioning at boot.

Acceptance

• A workspace Location whose directory does not exist on the server host constructs its full service graph.
• Local symlink canonicalization behavior unchanged.

Found during #44554 (see PR #44560, which fixed liveness eviction only). Part of the boot-cycle process-vs-workspace audit alongside #44552, #44553, #44555.

Start in packages/core/src/filesystem.ts at line 66 and trace how FileSystem resolves location.directory during Location boot. Compare workspaceID placements with local locations, then verify that a workspace directory absent from the server host can construct its full service graph without provisioning at boot while local symlink canonicalization remains unchanged.