ci: move perf gate and changelog onto the soothfast action

.github/workflows/ci.yml

@@ -18,3 +18,23 @@ jobs:
       - run: cargo fmt --all -- --check
       - run: cargo clippy --workspace --all-targets -- -D warnings
       - run: cargo test --workspace
+
+  soothfast:
+    # the bot's own merge must not regenerate again
+    if: github.event_name == 'pull_request' || !endsWith(github.actor, '[bot]')
+    runs-on: ubuntu-latest
+    environment: soothfast-bot
+    permissions:
+      contents: read
+      pull-requests: write
+      id-token: write
+    concurrency:
+      group: soothfast-${{ github.ref }}
+      cancel-in-progress: true
+    steps:
+      - uses: actions/checkout@v5
+      - uses: dtolnay/rust-toolchain@stable
+      - uses: Swatinem/rust-cache@v2
+      - uses: Verdenroz/soothfast@80b18d8831521646b65fec79c6df14d6f763c602 # v0.3.1
+        with:
+          changelog-packages: scry-core scry-server

.github/workflows/docs.yml

@@ -20,7 +20,11 @@ jobs:
       - uses: Swatinem/rust-cache@v2
       # callgrind fallback for PMU-less runners
       - run: sudo apt-get update -qq && sudo apt-get install -y -qq valgrind
-      - run: cargo install cargo-soothfast --locked
+      # install only, pinned to Cargo.lock
+      - uses: Verdenroz/soothfast@80b18d8831521646b65fec79c6df14d6f763c602 # v0.3.1
+        with:
+          gate: "false"
+          changelog: "false"
       - run: cargo soothfast measure -p scry-core --save-baseline base
       - run: cargo soothfast docs check
       - run: cargo soothfast docs build --baseline base

CLAUDE.md

@@ -12,7 +12,7 @@ cargo clippy --workspace --all-targets -- -D warnings   # CI treats warnings as
 cargo fmt --all
 
 cargo soothfast measure -p scry-core --save-baseline base   # refresh perf baseline
-cargo soothfast gate -p scry-core --against-ref origin/main # what gate.yml runs on PRs
+cargo soothfast gate -p scry-core --against-ref origin/main # what CI runs on PRs
 cargo soothfast docs check                   # doc claims vs the "base" baseline
 cargo soothfast docs build --baseline base   # site to ./site (published by docs.yml)
 
@@ -94,8 +94,12 @@ installed copies until the version is bumped in BOTH
 `crates/scry-core/benches/soothfast.rs`; `docs/search.md` carries claims
 checked against the `base` baseline (alloc claims are exact - changing a
 measured function usually means re-measuring and updating the claim);
-`gate.yml` measures PRs against their merge-base, so perf regressions in
-measured functions fail CI by design, not by flake.
+the `soothfast` job in `ci.yml` (the `Verdenroz/soothfast` action) gates PRs
+against their merge-base and posts the result as a soothfast-bot comment, so
+perf regressions in measured functions fail CI by design, not by flake. On
+pushes to `main` the same job refreshes the baseline and lands CHANGELOG.md
+as a `bot/soothfast-update` PR. Bump the action ref together with the
+`soothfast` dependency; the action installs the CLI matching `Cargo.lock`.
 
 ## Config
 

crates/scry-core/Cargo.toml

@@ -40,5 +40,5 @@ tree-sitter-typescript = "0.23.2"
 xxhash-rust = { version = "0.8.18", features = ["xxh64"] }
 
 [dev-dependencies]
-soothfast = { version = "0.2.0", features = ["runner"] }
+soothfast = { version = "0.3.1", features = ["runner"] }
 tempfile = "3.27.0"

crates/scry-core/benches/soothfast.rs

@@ -76,10 +76,13 @@ fn bench_chunk_rust(source: &str) {
     keep(scry_core::chunker::chunk_file("bench.rs", keep(source)));
 }
 
+// Small enough that harness/codegen noise straddles the default threshold
+// run-to-run.
 #[bench(
     group = "search",
     setup = symbol_table,
-    covers = "scry_core::search::expand_symbols"
+    covers = "scry_core::search::expand_symbols",
+    tolerance = "8%"
 )]
 fn bench_expand_symbols(symbols: &[String]) {
     keep(scry_core::search::expand_symbols(