fix(skills): validate registry keys before using them as cache directories

Cause: sync_one_skill joined the registry index key straight onto the skill
cache directory and later removed, renamed and wrote under it, while the
installed-skill path already ran validate_skill_name_segment.

Fix: run validate_skill_name_segment on the key first and report a Failed
outcome for a key that is not one path-safe segment.

Test: registry_sync_refuses_a_key_that_is_not_a_single_segment (`../escape`,
`..`, `a/b`, `/abs`); fails with the check disabled (1 failed).
- cargo test -p codewhale-tui --lib -- skills::install:
  test result: ok. 21 passed; 0 failed

Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>

CHANGELOG.md

@@ -178,6 +178,9 @@ quieter, and Fleet runs can be checked before they spend anything.
 - Computer Use: screenshot and zoom output paths must be `.png`/`.jpg`/`.jpeg`
   files inside the recordings directory, and zoom always crops the last
   captured raster instead of a caller-named source file.
+- Skill registry sync refuses an index key that is not a single path-safe
+  name before it is used as a cache directory, the same check an installed
+  skill name already gets.
 
 ### Removed
 

crates/tui/CHANGELOG.md

@@ -178,6 +178,9 @@ quieter, and Fleet runs can be checked before they spend anything.
 - Computer Use: screenshot and zoom output paths must be `.png`/`.jpg`/`.jpeg`
   files inside the recordings directory, and zoom always crops the last
   captured raster instead of a caller-named source file.
+- Skill registry sync refuses an index key that is not a single path-safe
+  name before it is used as a cache directory, the same check an installed
+  skill name already gets.
 
 ### Removed
 

crates/tui/src/skills/install.rs

@@ -656,6 +656,14 @@ async fn sync_one_skill(
     cache_dir: &Path,
     max_size: u64,
 ) -> SkillSyncOutcome {
+    // The registry key names the cache directory joined below; it gets the
+    // same single-segment check as an installed skill name.
+    if let Err(err) = validate_skill_name_segment(name) {
+        return SkillSyncOutcome::Failed {
+            name: name.to_string(),
+            reason: format!("{err:#}"),
+        };
+    }
     // Resolve the source to a concrete URL list.
     let source = match InstallSource::parse(&entry.source) {
         Ok(s) => s,
@@ -1668,6 +1676,29 @@ fn hex_bytes(bytes: impl AsRef<[u8]>) -> String {
 mod tests {
     use super::*;
 
+    #[tokio::test]
+    async fn registry_sync_refuses_a_key_that_is_not_a_single_segment() {
+        let root = tempfile::tempdir().expect("tempdir");
+        let cache_dir = root.path().join("cache");
+        std::fs::create_dir_all(&cache_dir).expect("cache dir");
+        let entry = RegistryEntry {
+            source: "https://example.invalid/skill.tar.gz".to_string(),
+            description: None,
+            keywords: Vec::new(),
+            domains: Vec::new(),
+        };
+        for name in ["../escape", "..", "a/b", "/abs"] {
+            let outcome =
+                sync_one_skill(name, &entry, &NetworkPolicy::default(), &cache_dir, 1024).await;
+            assert!(
+                matches!(outcome, SkillSyncOutcome::Failed { ref reason, .. }
+                    if reason.contains("single path-safe segment")),
+                "{name}: {outcome:?}"
+            );
+        }
+        assert!(!root.path().join("escape").exists());
+    }
+
     #[test]
     fn parse_github_source() {
         let s = InstallSource::parse("github:Hmbown/test-skill").unwrap();