Fix install.sh error when cwd equals INSTALL_DIR (#10)

## Summary
- Fix `mv: 'binary' and 'target/binary' are the same file` error during
first-time install
- When strawhub runs `install.sh`, it sets cwd to the package directory
(same as `INSTALL_DIR`). The `mv` fails because source and destination
are the same file.
- Skip the `mv` when both paths resolve to the same absolute path

## Test plan
- [ ] Fresh install via `strawhub install` no longer shows the error

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: juhgiyo

strawpot_codex/install.sh

@@ -43,7 +43,12 @@ chmod +x "${BINARY_NAME}"
 mkdir -p "$INSTALL_DIR"
 
 if [ -w "$INSTALL_DIR" ]; then
-  mv "${BINARY_NAME}" "${INSTALL_DIR}/${BINARY_NAME}"
+  # Skip mv when already downloaded into the install directory (e.g. strawhub sets cwd = INSTALL_DIR)
+  SRC="$(cd "$(dirname "${BINARY_NAME}")" && pwd)/$(basename "${BINARY_NAME}")"
+  DST="$(cd "$INSTALL_DIR" && pwd)/${BINARY_NAME}"
+  if [ "$SRC" != "$DST" ]; then
+    mv "${BINARY_NAME}" "${INSTALL_DIR}/${BINARY_NAME}"
+  fi
 else
   echo "Error: cannot write to ${INSTALL_DIR}" >&2
   exit 1