* Scope config snapshot to files inside the working tree
* Record excluded snapshot entries as placeholders instead of links
* Limit linked snapshot content to unmodified tracked files and tracked directories
File targets reached through a link are included only when their content is
unchanged from HEAD, and directory targets only when they contain tracked
files; anything else is recorded as a single placeholder. Adds tests for a
sensitive path that links to a tracked directory, links to untracked
directories, and links to tracked files modified after checkout.
When snapshotting PR-authored sensitive paths into .claude-pr/, cpSync with
dereference:true throws ENOENT if a symlink target is missing on the PR head
(e.g. .claude/CLAUDE.md -> ../AGENTS.md). Fall back to copying the symlink
itself so restoreConfigFromBase can continue and restore trusted base versions.
Fixes#1398
