Address second review pass: fix start-time race + minor cleanups

- M1 (race): don't mount the host AWS dir for static-credential Bedrock.
  sync_bedrock_credentials() is the sole writer of ~/.aws/credentials in
  that mode, and mounting /tmp/.host-aws let the entrypoint's
  `rm -rf ~/.aws; cp -a` race that write at startup (only when a global
  aws_config_path was also set). Static keys + AWS_REGION env are
  self-sufficient and don't need the host config, so skipping the mount
  removes the dual-writer entirely.
- L-a: exit codes are now read via wait_for_exec_exit(), which polls
  inspect_exec until the exec reports finished, so a non-zero tar/cred
  exit isn't missed by reading exit_code too early. The backup only fails
  on a definitively non-zero code (falls back to the empty-output check
  if undeterminable).
- L-b: fixed two comments that referenced the old
  write_bedrock_static_credentials name (now sync_bedrock_credentials).
- L-c: entrypoint only rewrites ~/.claude.json when awsAuthRefresh is
  actually present, avoiding a needless jq reformat on every non-SSO
  start.
- L-d: backup script traps EXIT to remove its mktemp staging dir even
  when tar fails, so failed backups don't accumulate temp dirs (with the
  sanitized config copy) in the container.

L-e (drop routing) is a non-issue: the layout is tabbed, so only one
terminal pane is ever visible; the active-guard routing is correct.

Verified the race fix, trap cleanup, grep guard, and exit-code polling.
cargo check / tsc / vitest all pass.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

container/entrypoint.sh

@@ -231,7 +231,9 @@ if [ -n "$AWS_SSO_AUTH_REFRESH_CMD" ]; then
     chown claude:claude "$CLAUDE_JSON"
     chmod 600 "$CLAUDE_JSON"
     unset AWS_SSO_AUTH_REFRESH_CMD
-elif [ -f "$CLAUDE_JSON" ]; then
+elif [ -f "$CLAUDE_JSON" ] && grep -q '"awsAuthRefresh"' "$CLAUDE_JSON" 2>/dev/null; then
+    # Only rewrite when the key is actually present, to avoid a needless jq
+    # reformat of ~/.claude.json on every start of a non-SSO backend.
     MERGED=$(jq 'del(.awsAuthRefresh)' "$CLAUDE_JSON" 2>/dev/null)
     if [ -n "$MERGED" ]; then
         printf '%s\n' "$MERGED" > "$CLAUDE_JSON"