Proposal: show Codex thread names in Sessions

[uttamdeb]

CodeBurn's Sessions report currently falls back to a Codex session ID when the rollout has no title. Codex also writes thread names to $CODEX_HOME/session_index.jsonl as id/thread_name rows, including later rename rows.

Proposed scope: use the latest valid indexed name for active and archived Codex rollouts. Resolve it when serving the report so a rename appears even with a warm usage cache. Treat the index as advisory: missing or malformed rows fall back to the existing title/ID, and bound and sanitize display text. This is read-only and does not change token or cost accounting.

I have a local branch with cold/warm cache, rename, archived, missing-index, and malformed-row tests. The full root test suite passes on that branch and on main.

Would this scope be welcome as a small PR? Is there a relevant issue you would prefer me to reference, or can this discussion serve as the scope confirmation?

[uttamdeb]

Now that #1582 has merged, I can take this on as my next PR. Is the proposed read-only session_index.jsonl title lookup scope welcome? I will refresh the branch against current main and revalidate it before opening a PR. A maintainer confirmation here would help me follow CONTRIBUTING.md.

[uttamdeb]

Filed this as feature request #1625 now that issue creation is available. It retains the read-only lookup and warm-cache rename scope described here. Please use the issue for maintainer scope confirmation; I will wait before taking it forward.