fix: preserve signature notifications across transaction retries

[bmuddha]

What changed

Resending a transaction can currently give a signature subscriber AlreadyProcessed instead of the transaction's execution result. This change keeps submission errors separate from signature notifications, so retries cannot consume observers.

The common schedule() path still allocates no completion channel. Publishing updates when nobody is subscribed now skips the subscription map entirely, for signatures as well as persistent streams.

Closes #148

Impact

execute() receives submission errors directly; schedule() remains queue-only. Duplicate and invalid-blockhash rejections no longer appear as execution status. Rejected signatures still retain their deduplication reservation until expiry.

MBV #1710 tracks the consumer-side work. Stored and replicated formats are unchanged.

Reviewer notes

A subscriber joining during commit must not fall between notification and status lookup. Registration happens before the lookup, and commit makes the result readable before notifying subscribers.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: ASSERTIVE

Plan: Advanced

Run ID: 5b286f69-231b-41c2-b1ef-b19be4ec4372

📥 Commits

Reviewing files that changed from the base of the PR and between 39aacda and 4ace04b.

📒 Files selected for processing (17)

• README.md
• engine/README.md
• engine/src/accessor.rs
• engine/tests/transactions.rs
• keeper/README.md
• keeper/src/accessor.rs
• keeper/src/subscriptions.rs
• keeper/src/tests/recovery.rs
• keeper/src/tests/subscriptions.rs
• nucleus/README.md
• nucleus/src/runtime.rs
• processor/README.md
• processor/src/executor.rs
• processor/src/sequencer/mod.rs
• processor/src/sequencer/order.rs
• processor/src/sequencer/tests.rs
• processor/src/tests.rs

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📝 Walkthrough

Walkthrough

The change adds optional request-owned completion channels to transaction requests. execute receives admission or committed execution results, while schedule acknowledges queueing without a completion channel. Keeper separates admission rejection from signature-result fanout, caches committed results before notification, and updates subscription storage. Processor components propagate replies through ordering and execution. Tests and documentation cover retries, retained results, rejected transactions, and lease retention.

Priority: ➖ Normal

Change: Bug fix · Severity of issue fixed: Medium

Merge Risk: ⚪ Minimal · up to 4ace0

The transaction reply and subscription changes appear internally consistent and ready to merge after normal checks.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the main change: preserving signature notifications when transactions are retried.
Description check	✅ Passed	The description directly explains the changes to retries, submission errors, signature notifications, schedule behavior, and subscription handling.
Linked Issues check	✅ Passed	The changes satisfy the coding requirements in [#148]. execute() uses a request-owned oneshot reply for admission errors or the committed execution result. schedule() sends no reply channel and do…
Out of Scope Changes check	✅ Passed	The changes remain within [#148]. Runtime request plumbing, sequencer handling, executor replies, subscription storage, deduplication tests, recovery updates, and documentation directly support reques…
Docstring Coverage	✅ Passed	Docstring coverage is 96.15% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 52 functions across 12 files. (5 skipped: 5…

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