Collector 0.7.49: bounded Codex capture (#454) and proof IPC fix (#455)

Collector 0.7.49 keeps Codex capture moving on machines with large Codex backlogs, and makes the proof suite steadier.

• Codex capture keeps moving on large backlogs (#454). The collector reads big Codex session files in bounded slices, so new usage keeps arriving while a large backlog is read.
• Steadier proofs (#455). Proof child processes run without the tsx command-line IPC pipe, which removes a random "address already in use" failure in CI. The runtime is unchanged by this item.

Updating and rolling back:

• Rolling back to 0.7.48 or 0.7.47 keeps every usage row. In the named-usage rollback test, the released 0.7.48 and 0.7.47 readers reopened a ledger sealed by 0.7.49 after its lease expired, and no usage was dropped.

Runtime CLI SHA256: 35313c96a999b54fb839002f073784b836abaf3f8a3db918176caaf8481185aa.

Qualification: typecheck, the proof suite and system end-to-end qualification ran on the merged commit, on our own macOS runners. Two proofs that drive the real launchd and collector supervision are local-only on those runners, because the runners run a live collector (eco-6hoxj.165.179). 0.7.49 changes no launchd, install or supervision code. The published package is the qualified artifact from that run.