[integration-tests] port proptests to hegel state machines

[sunshowers]

The newest versions of hegel no longer need uv or Python so I feel much better porting over the tests to this model.

The commit is written slightly weirdly to try and preserve as much blame as possible. The next commit will fix up the indents and remove the shadow bindings (let map = &mut self.map), etc, with the idea that it'll be listed in .git-blame-ignore-revs.

Also update the MSRV to 1.86 since Hegel requires this.

[Copilot]

Pull request overview

Ports the integration property tests from proptest/test-strategy strategies to Hegel state machines, adds shared Hegel drawing helpers, and bumps the workspace MSRV to Rust 1.86 (including CI/docs/badges).

Changes:

• Replaces several integration proptests with #[hegel::state_machine]-based stateful tests and introduces hegel_support utilities for generating keys/items.
• Refactors panic-safety test infrastructure in iddqd-test-utils to remove proptest-generated op sequences and align with the new Hegel-based approach.
• Updates MSRV to Rust 1.86 across workspace metadata, docs, and CI.

Reviewed changes

Copilot reviewed 15 out of 17 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
crates/iddqd/tests/integration/tri_hash_map.rs	Migrates TriHashMap integration proptests to Hegel state machines + Hegel-based serde proptests.
crates/iddqd/tests/integration/main.rs	Registers the new hegel_support integration test module.
crates/iddqd/tests/integration/id_ord_map.rs	Migrates IdOrdMap integration proptests (including panic-safety) to Hegel state machines.
crates/iddqd/tests/integration/id_hash_map.rs	Migrates IdHashMap integration proptests (including panic-safety) to Hegel state machines.
crates/iddqd/tests/integration/hegel_support.rs	New shared generators/draw helpers for Hegel-based integration tests.
crates/iddqd/tests/integration/bi_hash_map.rs	Migrates BiHashMap integration proptests (including panic-safety) to Hegel state machines.
crates/iddqd/src/lib.rs	Updates documented MSRV to 1.86.
crates/iddqd/README.md	Updates MSRV badge and MSRV documentation text to 1.86.
crates/iddqd/Cargo.toml	Adds Hegel dependency for integration tests.
crates/iddqd-test-utils/src/test_item.rs	Removes permutation strategy helper previously used by proptest-based tests.
crates/iddqd-test-utils/src/panic_safety.rs	Removes proptest op-sequence types/constants; updates docs and observation labeling.
crates/iddqd-test-utils/src/naive_map.rs	Exposes items() accessor for Hegel lookup draws.
CHANGELOG.md	Notes MSRV bump in Unreleased section.
Cargo.toml	Bumps workspace rust-version to 1.86 and adds Hegel dependency to workspace deps.
Cargo.lock	Locks new transitive dependencies introduced by Hegel.
.gitignore	Ignores Hegel failure database directory (.hegel/).
.github/workflows/ci.yml	Updates CI MSRV runner version(s) to 1.86.

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