Absorb redundant atom-only SSA ternaries

[Kuhai9801]

Motivation

Closes #29343.

Builds on the SSA const propagation alias-forwarding change.

After SSA and earlier simplification, nested ternaries can remain in the shape:

let tmp = cond ? a : b;
return cond ? tmp : b;

or the symmetric false-branch form. When both ternaries use the same SSA condition and the tracked arms are atom-only, the inner temporary can be absorbed without dropping fallible work.

This PR extends SsaConstPropagation to:

• track local bindings to atom-only ternaries
• absorb true-branch and false-branch redundant nesting forms
• require matching SSA conditions and matching retained arms
• leave different conditions or different branch values unchanged
• compare literal atoms as well as SSA path atoms

It also restricts generated-Aleo redundant ternary absorption to the same safety boundary by tracking prior ternaries only when the condition and arms are registers or literals. That prevents the peephole pass from substituting member-access, array-access, tuple, or raw-name operands from an earlier ternary into a later one.

Test Plan

Added/updated regression coverage:

• ssa_const_propagation/nested_ternary_absorption
• compiler/peephole/ternary_absorption
• peephole unit coverage for atom operands and non-atom operands
• compiler expectation updates for storage aggregate cases where non-atom generated-Aleo operands are no longer absorbed

Verification performed:

• git diff --check
• conflict-marker scan over changed files
• merge simulation onto the SSA aggregate alias forwarding branch
• CircleCI PR checks

Related PRs

Part of the #29343 optimizer cleanup series.

Related PRs:

• Forward aliased aggregate fields in SSA const propagation #29543
• Forward repeated finalize storage reads #29545