sync-versions: exclude git-fetched upstream sources from Cat 1 sync

Cat 1 discovery treated every local/recipes/*\/source/Cargo.toml as an
in-house crate, including git-fetched upstream sources like brush
(git = github.com/reubeno/brush). Rewriting upstream crate versions to
the branch version broke upstream-internal version requirements
(brush-shell was forced to 0.3.1 while brush required ^0.4.0 —
'failed to select a version for the requirement brush-shell = ^0.4.0').

Guard: skip any crate whose Cargo.toml is not tracked by the parent
repo. In-house crates are tracked trees (no independent .git); fetched
sources are gitignored and untracked. Restores correct classification:
75 crates checked (12 fetched-source crates now excluded), drift 0,
brush cooks successfully again.

local/scripts/sync-versions.sh

@@ -104,6 +104,16 @@ should_exclude() {
         [[ "$path" == *"$ex"* ]] && return 0
     done
 
+    # Skip git-fetched upstream sources. Fetched recipe sources (e.g. brush
+    # from github) live in gitignored, untracked source/ trees; their crate
+    # versions belong to upstream, not to the Cat 1 in-house branch-version
+    # policy. Rewriting them breaks upstream-internal version requirements
+    # (this happened: brush-shell was forced to 0.3.1 while brush required
+    # ^0.4.0, breaking the build). In-house crates are tracked trees.
+    if ! git ls-files --error-unmatch "$path" >/dev/null 2>&1; then
+        return 0
+    fi
+
     return 1
 }