fix: accumulated values lost when reused tracked fn skips re-execution

[SAY-5]

When a tracked fn's inputs haven't changed, maybe_changed_after_cold fast-paths through deep_verify_memo and returns the VerifyResult directly. That result carries the accumulated flag from the fn's edge inputs only; if the fn itself pushed accumulated values, those are ignored. Callers upstream then see Empty and skip traversing this subtree, so accumulated values are silently dropped.

Fix: after deep_verify succeeds, check whether the memo's own AccumulatedMap is non-empty and return Any in that case, matching what the re-execute path already does (lines 229-232).

Fixes #923.

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[codspeed-hq]

Merging this PR will improve performance by 5.82%

⚡ 1 improved benchmark
✅ 25 untouched benchmarks

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚡	Simulation	amortized[InternedInput]	2.1 µs	2 µs	+5.82%

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Curious why this is faster? Comment @codspeedbot explain why this is faster on this PR, or directly use the CodSpeed MCP with your agent.

---

_{Comparing SAY-5:fix-accumulator-wrongresult-issue-923 (b928af4) with master (e4ae47b)}

[MichaReiser]

Let's avoid the unreachable here

Suggested change

	}
	if let VerifyResult::Unchanged { accumulated } = deep_verify {
	// Check if the inputs are still valid. We can just compare `changed_at`.
	return Some(if old_memo.revisions.changed_at > revision {
	VerifyResult::changed()
	} else {
	// Propagate accumulated values from inputs *and* from this memo itself.
	// Without the own-accumulated check, a caller querying accumulated values
	// would see `Empty` and skip traversing into this subtree even though
	// this memo directly pushed accumulated values.
	VerifyResult::unchanged_with_accumulated(
	#[cfg(feature = "accumulator")]
	{
	if old_memo.revisions.accumulated().is_some() {
	InputAccumulatedValues::Any
	} else {
	accumulated
	}

[SAY-5]

Destructured deep_verify directly so the cfg-gated accumulated binding falls out of the if-let, dropping the unreachable (b928af4). Local cargo test on accumulate*, accumulated_backdate, cycle_accumulate all green with --features accumulator.