fix: adversarial review fixes (Claude + Codex cross-model passes)

Both adversarial passes ran against the wave; every FIXABLE finding landed
with a regression test:

- probeTimeoutMs clamps to >=1ms: a fractional override floored to 0, and
  execFileSync treats timeout:0 as NO timeout — the probe that exists to
  bound hangs could hang forever (found by both models independently).
- /ship silent hook install now requires the hooks dir to live inside
  .git: with core.hooksPath (husky's COMMITTED .husky/), the chaining
  installer would have renamed the team's committed pre-push and written a
  machine-local wrapper into the working tree (found by both models).
- gstack-config gbrain-refresh accepts the "timeout" status — the last
  consumer still gating on literal "ok" (Codex); gstack-gbrain-detect's
  config-derived fields honor GBRAIN_HOME so the detection JSON can't
  report status ok alongside config_exists false (Codex).
- prepush: a remote sha absent locally (shallow clone / stale fetch) falls
  back to the merge-base/empty-tree range — scans MORE, never blocks a
  legitimate push into training users toward --no-verify.
- dashboards: curl's own 000 no longer doubles to "HTTP 000000"; the
  community dashboard flags stale snapshots like the security one; array
  sections parse via jq (the sed/grep loops truncated at the first ']');
  the no-jq marker grep tolerates whitespace.
- telemetry: multi-line redactor output nulls the field instead of
  corrupting the JSONL record; setup's hint fires only when the config key
  is genuinely unset (an explicit false is a recorded decline); the /ship
  prompt marker honors GSTACK_HOME.

Kept as designed (cross-model tension noted): Bearer stays MEDIUM in the
prepush gate — a HIGH Bearer would block every docs example; the entropy
validator can't eliminate that FP class, and MEDIUM warns visibly.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

bin/gstack-telemetry-log

@@ -200,7 +200,9 @@ if (out === null) process.exit(1);
 console.log(JSON.stringify(out.slice(0, 200)));
 " 2>/dev/null)" || ERR_MSG_FIELD="null"
   case "$ERR_MSG_FIELD" in
-    \"*\") ;; # JSON string — safe to embed
+    *"
+"*) ERR_MSG_FIELD="null" ;; # embedded newline would corrupt the JSONL record
+    \"*\") ;; # single-line JSON string — safe to embed
     *) ERR_MSG_FIELD="null" ;;
   esac
 fi