v2.3.5 — critic-gemini stderr JSON fix

Fixed

• critic-gemini.sh stderr noise broke JSON parsing (#17): gemini output was captured with 2>&1, merging the CLI's terminal-capability warnings ("True color (24-bit) support not detected", "Ripgrep is not available…") into the JSON on stdout, so jq -e . failed and the wrapper exited 1 — silently disabling the cross-model critic (gemini-only / dual-CMC modes). Now captures stderr to a tempfile (surfaced only on real invocation failure) and adds a line-based pre-JSON guard (awk '/^[[:space:]]*\{/{f=1} f') as defense-in-depth for gemini-cli #21433 (startup messages leaking to stdout). Regression coverage: hooks/tests/critic-gemini.bats (5 tests, incl. brace-in-string non-truncation).

Full Changelog: v2.3.4...v2.3.5