fix(install): install jq prerequisite (active hooks require it)

jq is used 18+ times in always-on hooks (statusline.sh, rtk-rewrite.sh)
but was never installed by any script — it only worked because dev
machines happened to have it; a bare machine breaks at hook-run time.
Add it to Step 1 (same inline pattern as the other prereqs) and to
doctor.sh at fail level.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UyNYwD4UccVw9ZCFZyJX55

doctor.sh

@@ -127,6 +127,12 @@ else
   fail "Node.js not found"
 fi
 
+if command -v jq &>/dev/null; then
+  pass "jq $(jq --version 2>/dev/null | sed 's/^jq-//')"
+else
+  fail "jq not found — statusline & rtk-rewrite hooks require it"
+fi
+
 if command -v cargo &>/dev/null; then
   pass "Cargo $(cargo --version | awk '{print $2}')"
 else