docs: clarify public project overview

[jmcte]

Summary

• Clarifies the README opening so it reflects the current read-only local inventory command surface.
• Fixes the README read-surface sentence for Safari, iCloud Drive, and Shortcuts metadata.

Issue

No open governing issue; this is a docs-only public-readiness cleanup found during branch/doc audit.

Validation

• bash scripts/ci/run-fast-checks.sh passed outside the sandbox after the sandboxed run hit Swift module-cache permissions.
• The successful gate covered privacy checks, Swift tests, debug build, release build, and CLI help output.

Risks / Notes

• Docs-only change.
• No runtime behavior changes.

[athena-omt]

I could not complete the PR review because the required worker-node worktree is unavailable. The required path /openclaw-data/src/_worktrees/athena/omt-global/icloud-cli/pr-43 is missing, /openclaw-data is not mounted on this host, creating it failed with permission denied, and passwordless sudo is unavailable. Per the review routing rules, I did not fall back to coordinator-path or source-only inspection. Please reroute this review to the Athena worker with /openclaw-data mounted or prepare the required worktree there, then rerun the review.