fix: use ZZ as IonQ Forte native 2Q gate instead of MS

[splch]

Summary

• IonQ Forte Enterprise 1 rejects the ms gate with "Gate types [ms] are not supported by this backend". Its native 2Q entangling gate is zz, confirmed by the compilation output (gate_basis: "ZZ") and successful hardware execution with custom pulse shapes.
• Adds gate.ZZ(theta) constructor, builder shorthand, ZZ-basis decomposition rules, and updates IonQForte target from [GPI, GPI2, MS] to [GPI, GPI2, ZZ]. Aria retains MS.
• Fixes pre-existing op-ordering bugs in decompose1qToIonQ(H) and rzToIonQ where ops were in math-notation order instead of circuit-execution order (never caught because the MS CNOT path uses a hardcoded sequence).

Test plan

• TestMarshalZZGate verifies ZZ serializes to "zz" with angle in turns
• TestDecomposeByRule_CNOT_ToZZBasis verifies CNOT decomposition to GPI/GPI2/ZZ matches CNOT unitary up to global phase
• TestDecomposeByRule_CZ_ToZZBasis and _SWAP_ToZZBasis verify CZ and SWAP decompositions
• TestUnitarity now includes ZZ(pi/4)
• TestHasBasisGate_IonQ updated for ZZ in Forte, MS in negative set
• Full test suite passes (go test ./... - 0 failures)
• Validated on hardware: submitted native ZZ circuit with custom pulse shapes to qpu.forte-enterprise-1, job completed successfully

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Codecov Report

❌ Patch coverage is 49.47368% with 48 lines in your changes missing coverage. Please review.
✅ Project coverage is 71.42%. Comparing base (8d79612) to head (27a3bed).

Files with missing lines	Patch %	Lines
transpile/decompose/rules.go	41.25%	45 Missing and 2 partials ⚠️
circuit/builder/builder.go	0.00%	1 Missing ⚠️

❌ Your patch status has failed because the patch coverage (49.47%) is below the target coverage (70.00%). You can increase the patch coverage or adjust the target coverage.
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Additional details and impacted files

@@            Coverage Diff             @@
##             main      #37      +/-   ##
==========================================
- Coverage   71.46%   71.42%   -0.04%     
==========================================
  Files         166      166              
  Lines       17602    17695      +93     
==========================================
+ Hits        12579    12639      +60     
- Misses       4058     4088      +30     
- Partials      965      968       +3     

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