fix(chart): skip unused synastry overview and doomed report subprocesses

Synastry charts now skip the unused external overview and run together. Reports skip PyJHora subprocesses when that library is missing, and a full heavy-compute slot logs which paths hold it. Splitting quotas stays a simulation.

Gate, growth, and report pytest passed, as did the frontend route tests, tsc, lint, and the A/B script.

Co-Authored-By: Grok (agent loop)
Co-authored-by: Cursor <cursoragent@cursor.com>

docs/testing/api-chart-subprocess-gate-ab-20261013.json

@@ -0,0 +1,53 @@
+{
+  "charts": {
+    "serial_seconds_median": 8.0596,
+    "concurrent_skip_seconds_median": 0.0166,
+    "serial_subprocesses_median": 2,
+    "concurrent_skip_subprocesses_median": 0,
+    "summary_bytes_match": true
+  },
+  "report_forced_subprocess": {
+    "seconds_median": 16.5322,
+    "subprocesses_median": 7
+  },
+  "report_short_circuit": {
+    "seconds_median": 15.3235,
+    "subprocesses_median": 1
+  },
+  "report_bytes_match": true,
+  "schemes": [
+    {
+      "scheme": "O1",
+      "consult_429": "0.40",
+      "report_429": "0.00",
+      "score_429": "0.17",
+      "peak": 2,
+      "touches_bug_717": false
+    },
+    {
+      "scheme": "O2",
+      "consult_429": "0.00",
+      "report_429": "0.00",
+      "score_429": "0.17",
+      "peak": 3,
+      "touches_bug_717": true
+    },
+    {
+      "scheme": "O3",
+      "consult_429": "0.30",
+      "report_429": "0.00",
+      "score_429": "0.33",
+      "peak": 2,
+      "touches_bug_717": false
+    },
+    {
+      "scheme": "O4",
+      "consult_429": "0.00",
+      "report_429": "0.00",
+      "score_429": "0.67",
+      "peak": 2,
+      "touches_bug_717": false
+    }
+  ],
+  "jhora_installed": false
+}