feat(value): introduce Set storage abstraction

[anakrish]

Adds an opaque Set newtype paralleling Object, living under src/value/set/ with the same module structure as src/value/object/ (mod.rs / iter.rs / serde.rs).

Set wraps BTreeSet<Value> today but exposes only a curated surface: contains, insert, remove, iter / iter_sorted, cursor (resumable), is_subset, intersection, difference, serde, and a hand-written Ord. The cursor type is re-exported behind the rvm feature so the follow-up IterationState::Set swap can land additively.

To free the Set name for the new public type, the crate-internal BTreeSet as Set / HashSet as Set alias in lib.rs is renamed to MapSet. Only one in-tree consumer existed (compiled_policy::CompiledPolicy::rule_paths) and is updated in lockstep.

Value::Set is unchanged in this PR (still Rc<BTreeSet<Value>>); the payload swap and call-site migration ship in a follow-up PR.

Tests live in src/value/tests.rs alongside the Object tests.

[Copilot]

Pull request overview

Introduces a new opaque value::Set container (mirroring value::Object) to abstract set storage behind a curated API, while freeing the Set identifier by renaming the internal lib.rs collection alias to MapSet.

Changes:

• Added src/value/set/ (Set type, iterator wrappers, and serde support) and re-exported Set (and SetCursor behind rvm) from src/value/mod.rs.
• Updated the single in-tree consumer of the old crate-internal Set alias (CompiledPolicyData::rule_paths) to use MapSet.
• Added unit tests for Set behavior and serde round-trips; added docs/value/set.md describing the design.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/value/tests.rs	Adds test coverage for the new Set API (iteration, algebra, cursor, serde, COW behavior via Value::Set).
src/value/set/mod.rs	Implements the new Set abstraction, including cursor iteration and set algebra helpers.
src/value/set/iter.rs	Adds opaque iterator newtypes and IntoIterator impls for Set and &Set.
src/value/set/serde.rs	Implements Serialize/Deserialize for Set, with per-element memory-limit checks during deserialization.
src/value/mod.rs	Wires the new set module and re-exports Set (and SetCursor behind rvm).
src/lib.rs	Renames the crate-internal Set collection alias to MapSet to avoid colliding with the new public Set type.
src/compiled_policy.rs	Updates rule_paths storage type from Set<String> to MapSet<String>.
docs/value/set.md	Documents the new Set abstraction and intended backend-swappability.

[anakrish]

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[Copilot]

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated no new comments.