fix(ci): rust-ci.yml use --features verisim, not --all-features (#85)

--all-features force-enables flint/spark/chapel — deliberately opt-in,
system-library-dependent features (libflint LGPL-3, GNAT+libechidna_spark,
Zig FFI) that the default GitHub runner cannot link. This made Test
Suite / Code Coverage / MVP Smoke / Julia Integration fail on EVERY PR
(present on main; surfaced on #73) with:

  rust-lld: error: unable to find library -lflint

build.rs already gates -lflint behind cfg(feature="flint") correctly;
the defect was the workflow forcing the feature on. flint/spark/chapel
keep their dedicated CI (chapel-ci.yml, SPARK Theatre Gate, live-provers.yml).
verisim is the only pure-Rust optional feature → safe maximal set for
the bare-runner clippy/test/doc/MSRV steps.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

.github/workflows/rust-ci.yml

@@ -45,14 +45,20 @@ jobs:
       - name: Check formatting
         run: cargo fmt --all -- --check
 
+      # NOTE: use --features verisim, NOT --all-features. `flint`/`spark`/
+      # `chapel` are deliberately opt-in, system-library-dependent features
+      # (libflint LGPL-3 / GNAT+libechidna_spark / Zig FFI lib) that the bare
+      # runner cannot link. They have dedicated CI (chapel-ci.yml, the SPARK
+      # Theatre Gate, live-provers.yml). `verisim` is the only pure-Rust
+      # optional feature, so it is the safe maximal set here. (echidna#85)
       - name: Clippy lints
-        run: cargo clippy --all-targets --all-features -- -D warnings
+        run: cargo clippy --all-targets --features verisim -- -D warnings
 
       - name: Run unit tests
-        run: cargo test --lib --all-features
+        run: cargo test --lib --features verisim
 
       - name: Run integration tests
-        run: cargo test --test integration_tests --all-features
+        run: cargo test --test integration_tests --features verisim
 
       - name: Build release
         run: cargo build --release
@@ -133,7 +139,7 @@ jobs:
         uses: Swatinem/rust-cache@ad397744b0d591a723ab90405b7247fac0e6b8db # v2
 
       - name: Build documentation
-        run: cargo doc --no-deps --all-features
+        run: cargo doc --no-deps --features verisim   # see echidna#85 (no --all-features on bare runner)
         env:
           RUSTDOCFLAGS: -D warnings
 
@@ -202,4 +208,4 @@ jobs:
         uses: Swatinem/rust-cache@ad397744b0d591a723ab90405b7247fac0e6b8db # v2
 
       - name: Check MSRV
-        run: cargo check --all-features
+        run: cargo check --features verisim   # see echidna#85 (no --all-features on bare runner)