revert(ci): drop the kache experiment; restore rust-cache baseline

Measured on the pool (2026-08-13): kache-only (no rust-cache) ran the rust
job in 30.8 min vs the 27 min rust-cache baseline; kache + rust-cache was
38.1 min. The job is test-dominated (~20 min of ~27), so a compile cache
cannot win: kache removes the rust-cache restore but adds setup/post
overhead (binary download, daemon, warm prefetch, sync push, report).
R2 warm hits covered the compile phase and the result was still slower.

Revert to the proven configuration: Swatinem/rust-cache on the rust job,
no kache-action anywhere. The real fixes from this session stand: the
5 GiB VM memory ceiling (host OOM class) and the deaf-runner fixes
(bridge resilience + server liveness sweep, shipped in v0.30.2).
R2 bucket/secrets stay in place if a compile-heavy workload ever
justifies revisiting this.

Author: Bnjoroge1

.github/workflows/ci.yml

@@ -78,20 +78,8 @@ jobs:
           toolchain: "1.86"
           components: rustfmt,clippy
 
-      # Content-addressed compile cache shared through R2: the rust and
-      # property-tests jobs run in parallel on separate pool VMs and no
-      # longer compile the same crates twice, and a lockfile/toolchain bump
-      # only misses the crates that actually changed. Distinct manifest keys
-      # keep the two jobs' prefetch manifests from clobbering each other.
-      - uses: kunobi-ninja/kache-action@49398d37113c616fdb61be434cb497e3c2c8f3e6 # v1
-        with:
-          s3-bucket: preloop-kache
-          s3-endpoint: https://da4b337a84d48ad45633a546cd97dbff.r2.cloudflarestorage.com
-          s3-region: auto
-          s3-access-key-id: ${{ secrets.KACHE_R2_ACCESS_KEY_ID }}
-          s3-secret-access-key: ${{ secrets.KACHE_R2_SECRET_ACCESS_KEY }}
-          manifest-key: ci-rust
-          pr-comment: false
+      # inline run steps work against preloop
+      - uses: Swatinem/rust-cache@49a0bdc70d2e1b713ca9e2869b211fcce03d3c1c
 
       - run: cargo fmt --all --check
       - run: |
@@ -118,16 +106,6 @@ jobs:
         with:
           toolchain: "1.86"
 
-      - uses: kunobi-ninja/kache-action@49398d37113c616fdb61be434cb497e3c2c8f3e6 # v1
-        with:
-          s3-bucket: preloop-kache
-          s3-endpoint: https://da4b337a84d48ad45633a546cd97dbff.r2.cloudflarestorage.com
-          s3-region: auto
-          s3-access-key-id: ${{ secrets.KACHE_R2_ACCESS_KEY_ID }}
-          s3-secret-access-key: ${{ secrets.KACHE_R2_SECRET_ACCESS_KEY }}
-          manifest-key: ci-property-tests
-          pr-comment: false
-
       # Zero-filter guard so just fail if no properties match the filter
       - name: Verify concurrency_properties filter matches at least one test
         run: |

.github/workflows/release-golden.yml

@@ -143,18 +143,6 @@ jobs:
       - name: Set up Rust toolchain
         uses: dtolnay/rust-toolchain@4360b52568e2003a75bf9bc1d59f33a8e3fc893c
 
-      # Release builds are the slowest compiles on the pool; cache them
-      # through the shared R2 bucket so golden re-bakes skip them entirely.
-      - uses: kunobi-ninja/kache-action@49398d37113c616fdb61be434cb497e3c2c8f3e6 # v1
-        with:
-          s3-bucket: preloop-kache
-          s3-endpoint: https://da4b337a84d48ad45633a546cd97dbff.r2.cloudflarestorage.com
-          s3-region: auto
-          s3-access-key-id: ${{ secrets.KACHE_R2_ACCESS_KEY_ID }}
-          s3-secret-access-key: ${{ secrets.KACHE_R2_SECRET_ACCESS_KEY }}
-          manifest-key: golden-release
-          pr-comment: false
-
       - name: Build Preloop binaries
         run: |
           cargo build --release -p preloop-cli -p preloop-runner-server