Update Rust crate iddqd to 0.4

[oxide-renovate]

This PR contains the following updates:

Package	Type	Update	Change
iddqd	workspace.dependencies	minor	0.3 → 0.4

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Release Notes

oxidecomputer/iddqd (iddqd)

v0.4.2

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Fixed

• The retain callbacks no longer permit the RefMut to be stashed outside them. This is technically a breaking change, but is being treated as a soundness bugfix.
• A number of soundness and resilience fixes for pathological implementations. These were found through a combination of human-driven analysis, example-based tests with Miri, chaos testing using fault injection with proptest, and adversarial code review from Claude Opus 4.7 and GPT-5.5. In particular, iddqd now more consistently preserves internal map state across panics in user code by using patterns like prepare-then-commit, index-based cleanup, cached hashes, and careful ordering of user-code execution relative to internal mutations.

Changed

• MSRV updated to Rust 1.85.

v0.4.1

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Fixed

• Fixed a logic bug in TriHashMap::remove_unique, when key1 matches, and one of key2 and key3 matches, but not the other.

v0.4.0

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Changed

• The internal implementation for item storage has been changed to use a linear slot-based buffer, resulting in 2-3x performance improvements for most workloads.
• The maps now have a limit of u32::MAX (4 294 967 295) elements at any given time. This limit is very unlikely to be reached in practice.

Fixed

• All mutation methods for IdHashMap and IdOrdMap are now panic-safe, in the sense that a panic in user code will not corrupt the map. This does not currently extend to BiHashMap and TriHashMap

Added

• Many more unit and property-based tests covering various kinds of pathological user implementations. We now have high confidence that arbitraily buggy user implementations (as long as they're in safe Rust) will not result in undefined behavior.

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