[codex] Add quota spend forecasting

[xodapi]

Summary

• add quota burn-rate tracking for account-level rate limits
• expose burn rate and ETA fields in JSON snapshots
• show quota detail strings that warn when the account would hit the cap before reset
• ignore empty Codex rate_limits events so the UI does not render null pseudo-limits
• focus the quota panel on active agents, so Codex-only workspaces do not spend space on an empty Claude column
• clarify unknown quota states and add active/total/average token stats in the selected-session detail footer
• add --status-json, a compact privacy-preserving status payload for widgets/mobile clients

Why

Codex can report account quota windows in token_count events, but users need more than the current remaining percentage. A small burn-rate estimate makes it easier to see whether the current pace is safe or likely to hit the cap before the window resets.

The UI also benefits from treating Codex-only workspaces as a first-class case: when only Codex is active, the quota panel should prioritize Codex state and avoid showing an empty Claude half-column.

For lower-risk integrations such as mobile widgets, --status-json emits only aggregate health/quota fields and omits local paths, prompts, chat text, session identifiers, tool arguments, child commands, and project names.

Validation

• cargo check
• cargo test rate_limit_spend
• cargo test quota_
• cargo test status_summary
• cargo test readme_documents_json_snapshot_privacy_surface
• cargo test test_parse_codex
• cargo test codex_non_1m_context_window_does_not_show_1m_suffix
• cargo run -- --demo --status-json

Note: a full cargo test run on this Windows checkout still has unrelated existing collector test failures around temp/process/file ownership behavior; the new quota, UI, status summary, and Codex parser tests pass.