Codex chat can still show another session's conversation from weak screen evidence #2429

A plain Codex pane's chat can still show another session's conversation on main after #2426, from screen evidence that does not prove ownership. Reproduced by the merge pass's review of #2420 at 3552599c on plain (non-Kiro) Codex panes with isolated native stores and a fake herdr socket, the pane's own conversation stored in another folder and a peer thread in the pane's cwd:

1. No Codex process any more. When the final process lookup for the pane finds no Codex (it exited, or the screen is an earlier occupant's), the leftover screen text is still matched against this folder's threads and a peer thread is bound.
2. Long answers that differ only in punctuation. The long-answer match compares letters and digits only, so an answer saying a < b matches a screen showing a > b, and feature-one matches feature_one.
3. A tool call quoting another session's answer. A tool call's command line (for example • Ran printf "<another conversation's long answer>") and its indented └ output count as an assistant answer and bind that conversation.

Expected

Bind a pane only from evidence of its own Codex conversation: a running Codex process, and an answer shown as Codex shows it, symbols included. Prompts, queued messages and tool calls are not answers. When ownership cannot be proven, show the terminal.