Collector 0.7.50: recorded Codex tier reader (#458) and the studio5 session re-send fix (#460)

Collector 0.7.50 keeps a busy machine from re-sending every session, and gets ready to record how each Codex request was processed.

• No more full session re-sends behind one stuck session (#460). When one session couldn't be sent and had a large backlog of waiting rows, the collector looked at every row before skipping that session. On a busy machine that took longer than its time limit, so the collector fell back to re-sending every session, cycle after cycle. It now checks each waiting session once and stops at its first ready row. The same sessions are sent as before, and every waiting row is kept.
• Ready for the recorded Codex processing tier (#458). The collector now accepts and keeps a recorded Codex processing tier, whether written as serviceTier or service_tier, and keeps cached-input counts exactly as Codex stated them. This release doesn't write the tier yet. A later release turns that on, and this one is its safe rollback point.

Updating and rolling back:

• Rolling back to 0.7.49, 0.7.48 or 0.7.47 keeps every usage row. In the named-usage rollback test, the released 0.7.49, 0.7.48 and 0.7.47 readers each reopened a ledger sealed by 0.7.50 after its lease expired, and no usage was dropped.

Runtime CLI SHA256: 700e52f10899111b4372966a976a0e178ef57647590d41e2071a54f70c635251.

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). 0.7.50 changes no launchd, install or supervision code. The published package is the qualified artifact from that run.