docs: add Codecov badge, prepare Zenodo DOI badge slot, and fix CITATION

- README: add a live Codecov coverage badge (token wired up via repo
  Secrets in this round) and a commented-out Zenodo DOI badge that will
  be enabled once the first DOI is minted by the next GitHub release.
- CITATION.cff: the preferred-citation block had the wrong title (it
  pointed at the CTRA arXiv preprint while the URL pointed at the QQA
  ICLR 2025 paper). Replace the title with the correct ICLR 2025 paper
  ("Optimization by Parallel Quasi-Quantum Annealing with Gradient-Based
  Sampling") and add an arXiv:2409.02135 identifier so citation tooling
  (Zenodo, ORCID, OpenAlex) resolves to the same artefact.

Made-with: Cursor

Author: Yuma-Ichikawa

CITATION.cff

@@ -11,7 +11,7 @@ license: BSD-3-Clause
 version: 0.3.0
 preferred-citation:
   type: conference-paper
-  title: "Continuous Tensor Relaxation for Finding Diverse Solutions in Combinatorial Optimization"
+  title: "Optimization by Parallel Quasi-Quantum Annealing with Gradient-Based Sampling"
   authors:
     - family-names: Ichikawa
       given-names: Yuma
@@ -21,3 +21,7 @@ preferred-citation:
     name: "International Conference on Learning Representations (ICLR)"
   year: 2025
   url: "https://openreview.net/forum?id=9EfBeXaXf0"
+  identifiers:
+    - type: other
+      value: "arXiv:2409.02135"
+      description: arXiv preprint

README.md

@@ -14,6 +14,9 @@ methods, a 17-class problem catalogue, a Streamlit dashboard and a CLI.
   <a href="https://github.com/Yuma-Ichikawa/QQA4CO/actions/workflows/ci.yml"><img src="https://github.com/Yuma-Ichikawa/QQA4CO/actions/workflows/ci.yml/badge.svg" alt="CI"></a>
   <a href="https://yuma-ichikawa.github.io/QQA4CO/"><img src="https://img.shields.io/badge/docs-mkdocs--material-blue?logo=materialformkdocs&logoColor=white" alt="Documentation"></a>
   <a href="https://github.com/Yuma-Ichikawa/QQA4CO/discussions"><img src="https://img.shields.io/github/discussions/Yuma-Ichikawa/QQA4CO?logo=github&label=Discussions" alt="GitHub Discussions"></a>
+  <a href="https://codecov.io/gh/Yuma-Ichikawa/QQA4CO"><img src="https://codecov.io/gh/Yuma-Ichikawa/QQA4CO/branch/main/graph/badge.svg" alt="Coverage"></a>
+  <!-- Zenodo DOI badge: replace ZENODO_RECORD_ID once the first DOI is minted (see tasks/test/oss_followups_after_zenodo_codecov.md) -->
+  <!-- <a href="https://doi.org/10.5281/zenodo.ZENODO_RECORD_ID"><img src="https://zenodo.org/badge/DOI/10.5281/zenodo.ZENODO_RECORD_ID.svg" alt="DOI"></a> -->
 </p>
 
 <p align="center">