feat(otdf-sdk-mgr): add xtest feature detection context to subagent prompt (DSPX-3302)

Subagents now receive an explanation of why `supports <feature>` must be added
to the SDK CLI wrapper and how xtest uses it to activate dormant tests. Includes
the pattern for probing SDK capabilities and a reminder that the scenario(s) are
listed in the PR body.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: dmihalcik-virtru

otdf-sdk-mgr/src/otdf_sdk_mgr/cli_orchestrate.py

@@ -264,7 +264,27 @@ def ensure_subagent_settings(worktree: Path, repo_path: str | None) -> None:
 {body}
 --- END SPEC ---
 
-Instructions:
+## xtest feature detection
+
+The `tests` repo has a draft PR with dormant integration tests for this feature.
+The tests stay skipped until the SDK CLI wrapper reports support. xtest detects
+support by running:
+
+    <sdk-cli> supports {name}
+
+and expecting exit 0. Your todo list includes adding a `supports {name}` case
+to the SDK's `xtest/sdk/<lang>/cli.sh` wrapper. This is what activates the
+integration tests when your PR's CI runs — do not skip it.
+
+Look at existing `supports` cases already in the file for the pattern (they
+typically grep the SDK's own help or capability output for a feature string,
+e.g. `grep -q "mlkem:768" <<< "$(cli help ...)"` or a direct SDK call). The
+specific probe to use is noted in your todo list item.
+
+Related test scenario(s): {scenarios}
+
+## Instructions
+
 1. Implement every item in `repos.{cell_key}.todo`. Don't switch branches.
 2. Run the repo's local checks before committing (unit tests, linters, build).
 3. Commit using house-style subject: `<type>({path}): <description> ({jira})`.