Fix broken Eq/Ord consistency for AssetCapacity

[Copilot]

AssetCapacity derived PartialEq (float == semantics) while Ord used total_cmp, violating the Rust contract that a == b must imply a.cmp(&b) == Ordering::Equal. Concretely, Continuous(0.0) == Continuous(-0.0) was true but cmp returned Less.

Changes

• src/asset/capacity.rs: Remove PartialEq from #[derive]; add a manual impl PartialEq that delegates to self.cmp(other) == Ordering::Equal, aligning equality with total_cmp ordering:

impl PartialEq for AssetCapacity {
    fn eq(&self, other: &Self) -> bool {
        self.cmp(other) == Ordering::Equal
    }
}

• Tests: Add parameterised eq_consistent_with_ord cases covering the 0.0 vs -0.0 edge case, equal/unequal continuous, and equal/unequal discrete variants.
• Release notes: Add entry to docs/release_notes/upcoming.md.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Broken Eq/Ord semantics for AssetCapacity</issue_title>
<issue_description>AssetCapacity derives PartialEq (float == semantics) but implements Ord using total_cmp, and also declares Eq. This violates the required consistency between Eq/Ord and equality (e.g., 0.0 == -0.0 but total_cmp orders them differently; NaN also breaks reflexivity). Consider implementing PartialEq/Eq manually to align with total_cmp (or drop Ord/Eq if total ordering isn’t required).

Originally posted by @copilot in #1158 (comment)
</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Broken Eq/Ord semantics for AssetCapacity #1162

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[alexdewar]

This isn't the correct PR number. This PR is #1206. Fix the link and the text.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.03%. Comparing base (5389d44) to head (b442550).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1206   +/-   ##
=======================================
  Coverage   89.02%   89.03%           
=======================================
  Files          57       57           
  Lines        7838     7841    +3     
  Branches     7838     7841    +3     
=======================================
+ Hits         6978     6981    +3     
  Misses        564      564           
  Partials      296      296           

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