fix(agents): continue rule installation after target errors

agents/README.md

@@ -10,6 +10,7 @@ The primary workflow is to symlink files from here into each agent runtime/confi
 - `AGENTS.md`: global baseline rules for coding agents.
 - `evals/global-rules.md`: behavioral scenarios for validating changes to the global rules.
 - `install-rules.py`: installs the baseline by creating symlinks in supported agent config dirs.
+- `test_install_rules.py`: regression tests for file preservation and independent target handling.
 - `install-cli.md`: curated CLI install/update command snippets.
 - `install-skills.md`: curated `npx skills` command snippets.
 
@@ -38,6 +39,7 @@ Current targets:
 Behavior:
 
 - Each target is handled independently.
+- Target errors are reported while remaining targets are attempted; any error yields a nonzero exit.
 - Missing destination directories are skipped.
 - Existing regular files are preserved as `.bak` backups (numbered when a backup already exists).
 - Destination links are replaced atomically; a failed link creation leaves the destination intact.
@@ -49,6 +51,12 @@ the global rules source and is not installed by this script.
 Auto-approval controls tool prompting. The global rules still define task authorization, safety, and
 secret handling.
 
+Run installer regression tests without changing installed rules:
+
+```bash
+python3 -B -m unittest discover -s agents -p test_install_rules.py
+```
+
 ## About `install-cli.md` and `install-skills.md`
 
 Use them as snippet libraries: