[codex] Fix post-merge analytics integration failures (#27285)

## Why

Recent merges left `main` with analytics integration build failures.
Local Cargo runs also made the trimmed-skills test depend on
developer-installed skills, while Bazel used an isolated home.

## What changed

- Clone `thread_metadata.thread_source` when constructing goal analytics
event parameters.
- Group app-server thread extension inputs into
`ThreadExtensionDependencies`.
- Isolate the trimmed-skills test home so its exact fixture count is
stable across Cargo and Bazel.

## Validation

- `cargo check -p codex-analytics`
- `just test -p codex-analytics` (71 tests)
- `just test -p codex-app-server` (837 tests; one unrelated zsh-fork
timeout passed on retry)

codex-rs/analytics/src/reducer.rs

@@ -1300,7 +1300,7 @@ impl AnalyticsReducer {
                 thread_metadata.session_id.clone(),
                 connection_state.app_server_client.clone(),
                 connection_state.runtime.clone(),
-                thread_metadata.thread_source,
+                thread_metadata.thread_source.clone(),
                 thread_metadata.subagent_source.clone(),
                 thread_metadata.parent_thread_id.clone(),
             ),