feat: wal durability

[notxorand]

closes: #21

Greptile Summary

This PR introduces a custom write-ahead log and integrates durable source ingestion and cascade checkpoints into the inference runtime.

• Adds eventual and strict WAL durability modes, recovery, batching, pending-work tracking, and LWW-backed fact reads.
• Routes source mutations and rule-produced cascade outputs through durable checkpoints.
• Restores HLC state from persisted timestamps and adds storage configuration to the CLI and supervisor.
• Adds WAL and storage benchmarks plus persistence-focused tests.
• The latest revision makes failed strict-write rollback conditional on the timestamp originally published, preventing it from replacing a newer intervening fact.

Confidence Score: 5/5

No new actionable issue was established by the changes since the previous review, so the PR appears safe to merge.

The latest change guards strict rollback with the originally published timestamp, preventing failed writes from replacing a newer fact. All eight earlier Greptile threads were manually resolved without explanatory replies and therefore do not remain in the merge-safety scoring set.

Important Files Changed

Filename	Overview
src/wal.zig	Implements WAL serialization, recovery, asynchronous grouped writes, durability modes, fact state, pending work, cascade checkpoints, and timestamp-guarded rollback.
src/storage.zig	Delegates durable fact and pending-work operations to the custom WAL while retaining SQLite-backed module storage.
src/engine/context.zig	Adds persistence access, cascade accumulation, rollback bookkeeping, and checkpoint management to execution contexts.
src/engine/loop.zig	Drives inference from durable pending entries and commits cascade outputs together with the triggering acknowledgement.
src/engine/events.zig	Persists mapped source facts before execution, restores the HLC from durable state, and coordinates connector shutdown with the run loop.
src/memory/lww.zig	Adds independently owned rollback snapshots and complete ownership cleanup for values and causal-node strings.
src/wasm/host_abi/generic.zig	Makes reads safe across lock release and integrates rule-produced writes with cascade rollback and checkpointing.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    S[Source event] --> P[Persist source mutation]
    P --> W[WAL batch checkpoint]
    W --> D[Durable pending entry]
    D --> I[Inference loop]
    I --> L[Update in-memory LWW cache]
    L --> C[Accumulate cascade outputs]
    C --> F[Flush cascade checkpoint]
    F --> A[Acknowledge source pending entry]
    F --> R[Recover facts and pending work after restart]

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_{Reviews (5): Last reviewed commit: "fix: protect strict rollback state" | Re-trigger Greptile}

[codspeed]

Merging this PR will degrade performance by 14.58%

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

❌ 1 regressed benchmark
✅ 3 untouched benchmarks
🆕 1 new benchmark

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
❌	runtime.execution	7.4 s	8.6 s	-14.58%
🆕	runtime.storage	N/A	2.1 ms	N/A

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing wal-durability (5bc15e9) with dev (89658db)}