Research: define exact-workspace platform boundary

[joaomj]

Parent map: #1

Decision to resolve

Which repository structures, filesystem entry types, and metadata are included in TinyHarness exact undo across supported platforms?

Inputs

• Research: define the native compatibility baseline #5 native compatibility baseline
• Research: define worktree, undo, and completion semantics #6 worktree and exact undo semantics

Questions

Cover submodules, nested repositories, sparse checkout, special files, symlinks, executable bits, ACLs, xattrs, hard links, case behavior, and empty directories.

Output

A fail-closed support matrix and portable exactness contract.

Resolves when

TinyHarness can state exactly which workspaces it accepts and what exact restoration means on each supported platform.