Reduce integration test CI time from 2h37m by removing redundant test executions

[Stevengre]

Problem

Integration tests currently take 2h 37m (example run), which is too long for PR iteration.

Root Cause: Redundant Test Executions

Analysis of the test suite reveals significant overlap:

Test	Backend	Count	Wall Time	Purpose
test_exec_smir[*-haskell]	Haskell	35	~70 min	Concrete execution + snapshot
test_exec_smir[*-llvm]	LLVM	35	~55 min	Same, different backend
test_prove_termination	Haskell	19	~25 min	Prove termination (same 19 programs as exec_smir depth=None subset)
test_prove_rs	Haskell	49	long tail	Symbolic verification

Key redundancies:

1. exec_smir runs every test twice (LLVM + Haskell) — both verify the same snapshot output
2. prove_termination tests the exact same 19 programs already covered by exec_smir[*-haskell]
3. 9 out of 10 overlapping .rs files between prove-rs/ and exec-smir/ are byte-identical duplicates

Proposed Phased Approach

Phase 1: Remove redundant test runs (small PR, ~80 min savings)

1. exec_smir: keep Haskell only, remove LLVM parametrization
   • Haskell is the backend used for proving — bugs here have higher impact
   • Removing LLVM saves ~35 tests
2. Remove test_prove_termination entirely
   • exec_smir[*-haskell] already runs these 19 programs through the Haskell backend
   • prove_rs already covers symbolic verification

Expected result: ~2h37m → ~1h20m

Phase 2: Consolidate Rust test programs (structural refactor)

• Merge prove-rs/, exec-smir/, run-rs/ source files into a single programs/ directory
• Remove 9 duplicated .rs files
• Test logic references the unified directory

Phase 3: Declarative test configuration

• Introduce a config file (e.g., test-config.toml) mapping each program to its test modes (prove, run-haskell, parse-only)
• Single test function reads config and dispatches accordingly

More: Consolidate redundant tests

Data

134 unique Rust programs across 4 directories:

• prove-rs/: 84 .rs + 1 .json
• exec-smir/: 39 .rs
• run-rs/: 34 .rs (only used for smir-parse stability, not integration tests)
• run-smir-random/: 2 .rs

File overlaps: prove-rs ∩ exec-smir = 10 (9 identical), prove-rs ∩ run-rs = 13