fix: address code review findings across WS, CJK input, install.sh, and README

WebSocket route: add socket error handler to prevent process crashes, enforce
per-session connection limit (max 5), track/decrement counts on close.

CJK input: add destroy() method with proper listener cleanup, guard against
double-init, add maxlength/aria-label to textarea, use language-neutral
placeholder, explicitly clear cjkActive on hide.

install.sh: fix update() to use $BRANCH and $REPO_URL instead of hardcoded
origin/master — fork users were silently switched back to master on update.

README: fix broken markdown table (paragraph concatenated into last cell),
add CODEMAN_NODE_VERSION to env var table.

Tests: add 8 new test cases for batch coalescing, flush threshold, unknown
message types, connection limit, heartbeat, readyState guards. Import
MAX_INPUT_LENGTH from config, add connectWs timeout, replace setTimeout
with vi.waitFor in cleanup test.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

install.sh

@@ -1281,8 +1281,9 @@ update() {
 
     info "Updating Codeman..."
     cd "$INSTALL_DIR"
+    git remote set-url origin "$REPO_URL" 2>/dev/null || true
     git fetch --quiet origin
-    git reset --hard origin/master --quiet
+    git reset --hard "origin/$BRANCH" --quiet
     npm install --quiet --no-fund --no-audit 2>/dev/null || npm install --no-fund --no-audit
     npm run build --quiet 2>/dev/null || npm run build
     success "Updated to $(node -e "console.log(require('./package.json').version)")"