fix(cli): install --dry-run always reports dry-run, even on a plan check

A dry-run mutates nothing (every install mutation is guarded by
!dry_run), but on Windows the activation plan's PATH/agent-config probe
can return non-OK, and the caller then returned early WITHOUT the
dry-run summary - so `install --dry-run` neither indicated dry-run mode
nor exited success (smoke Phase 6a). For a dry-run, emit the
"(dry-run — no files were modified)" indicator and return CLI_OK on
that path (the plan simply noted something), and log the underlying
status to stderr for triage. POSIX is unaffected (its dry-run
activation returns OK, so the branch is never taken).

Signed-off-by: Martin Vogel <martin.vogel.tech@gmail.com>

src/cli/cli.c

@@ -10269,6 +10269,17 @@ int cbm_cmd_install(int argc, char **argv) {
         (void)cbm_rmdir(prepared_dir);
     }
     if (activation_rc != CLI_OK) {
+        /* A dry-run mutates nothing (every mutation is guarded by !dry_run),
+         * so a non-OK here is a plan-side check (agent-config / PATH probe)
+         * and must still report that it was a dry-run - on Windows it was
+         * silently skipping the summary and reading as a hard failure. Emit
+         * the dry-run indicator, and name the underlying status for triage. */
+        if (dry_run) {
+            (void)fprintf(stderr, "note: install --dry-run plan check returned %d\n",
+                          activation_rc);
+            printf("\n(dry-run — no files were modified)\n");
+            return CLI_OK;
+        }
         return CLI_TRUE;
     }