v3.0.0

• fix(tools): add error_kind to windows-gated bash ToolOutput literal
• chore(release): prepare v3.0.0 release
• feat(workspace)(sdk): typed ToolErrorKind end-to-end pipeline (Phase 8)
• feat(workspace)!: v3.0.0 — typed WorkspaceError on fs trait surface
• feat(workspace): WorkspaceError typed enum (additive; no signature changes)
• test(workspace): consolidate CAS test fixture onto InMemoryFileSystem
• test(workspace): backend conformance suite + InMemoryFileSystem reference
• fix(workspace): bound RemoteGit diff client-side via streaming + hard cap
• fix(workspace): with_remote_git no longer drops local_root or future fields
• perf(workspace): parallelize S3 grep via futures::buffer_unordered
• feat(workspace): implement mTLS for RemoteGitBackend
• feat(sdk): expose Phase 1-4 workspace options through Node + Python SDKs
• feat(workspace): RemoteGitBackend — HTTP/JSON git provider for cloud workspaces
• feat(workspace): S3 ls not-found semantics + per-call metering events
• feat(workspace): opt-in degraded grep/glob on S3 backend
• feat(workspace): optimistic concurrency for S3 edit/patch via ETag
• feat(workspace): enforce read_text size ceiling on S3 backend
• docs: README — direct tool methods + S3 workspace backend examples