fix(binance): isolate replay-safe capture epochs

[proerror77]

Change contract\nEach Binance websocket session is a fresh capture epoch, and only a safe scheduled rotation whose active books are all bridged and whose epoch archived a valid aggregate trade for every active symbol may seed replay-safe segment_open checkpoints at one pre-close rotation boundary.\n\nOut of scope\nBinance artifact verification and PR #120; cross-event aggregate-trade f/l continuity; downloader or OSS selection; research mapping; deployment, ECS, collector cutover, and live trading.\n\nDependency or merge order\nBased on main 44b554b after PR #119. Merge this producer contract before rebasing and finalizing PR #120.\n\nFocused validation\n- cargo test --locked -p hft-collector --features collector-binance --bin binance-lob-archiver: 36 passed\n- cargo test --locked -p hft-collector --features collector-binance: 159 library passed, 2 ignored; 36 archiver passed; 10 materializer passed; remaining bins passed\n- cargo clippy --locked -p hft-collector --all-targets --features collector-binance --no-deps -- -D warnings: passed\n- cargo fmt --package hft-collector -- --check: passed\n- git diff --check: passed\n- Red-to-green counterexamples cover per-symbol aggregate-trade coverage, unseeded rotation remaining unsafe after a later trade, and one pre-close timestamp shared by segment close/start/open.\n- Existing counterexamples cover snapshot-only epochs, trusted epochs without aggregate trades, reconnect-local state, and scheduled rotation seeding versus gap non-seeding.\n- Exact head 861335c: GitHub CI and CodeRabbit passed; independent Standards and Spec reviews found no issues; all review threads resolved.\n- Scope: one file, 403 insertions and 66 deletions, below the repository split threshold.\n\nRollout or rollback impact\nNo deployment or schema change. The producer changes only capture-epoch and segment-boundary replay safety. Reconnect, gap, exclusion, unseeded, and incomplete epochs remain fail-closed. Rollback is a revert of this PR; live trading remains disabled.

[coderabbitai]

📝 Walkthrough

Walkthrough

The archiver now tracks aggregate-trade observation in session-owned state. Segment rotation and closure use shared replay-readiness gating before seeding or writing checkpoints, and lifecycle tests cover the updated replay-safety behavior.

Changes

Replay checkpoint gating

Layer / File(s)	Summary
Session-owned aggregate-trade state rust_hft/tools/collector/src/bin/binance-lob-archiver.rs	run_session owns and propagates ProcessState, while aggregate-trade processing records observed symbols.
Replay-readiness checkpoint lifecycle rust_hft/tools/collector/src/bin/binance-lob-archiver.rs	Segment rotation and closure use shared readiness checks and centralized checkpoint writing to control replay safety.
Aggregate-trade gating test coverage rust_hft/tools/collector/src/bin/binance-lob-archiver.rs	Tests cover aggregate-trade setup and updated snapshot-only, trusted-epoch, and scheduled-rotation expectations.

Estimated code review effort: 4 (Complex) | ~45 minutes

Sequence Diagram(s)

sequenceDiagram
  participant run_session
  participant process_event
  participant rotate_segment
  participant replay_checkpoint_ready
  participant write_checkpoints
  run_session->>process_event: process aggregate-trade event
  process_event->>process_event: record observed symbol
  run_session->>rotate_segment: rotate with ProcessState
  rotate_segment->>replay_checkpoint_ready: evaluate replay readiness
  replay_checkpoint_ready-->>rotate_segment: readiness result
  rotate_segment->>write_checkpoints: write checkpoints when ready

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🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title is concise and accurately summarizes the main Binance replay-safety change.
Description check	✅ Passed	The description covers all required template sections with concrete validation, scope, dependency, and rollout details.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch codex/binance-capture-epoch

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