chore(toolchain): finish stable-migration cleanup in docs and query-regression pin

- README/AGENTS: the toolchain is now stable Rust pinned by
  rust-toolchain.toml, not nightly
- query-regression: align the benchmark toolchain pin with the
  workspace (nightly-2026-03-21 = 1.96.0-nightly -> stable 1.96.1),
  including the exact-version assertions (cargo 356927216, rustc
  31fca3adb, both 2026-06-26) and the runner image default

The query-regression runner image must be rebuilt and
QUERY_REGRESSION_ECS_IMAGE_ID bumped together with these pins
(per .github/runner-scale-sets/query-regression/README.md) before
the next regression run.

Part of #9289.

Signed-off-by: Ning Sun <sunning@greptime.com>

.github/runner-scale-sets/query-regression/Dockerfile

@@ -22,7 +22,7 @@ ARG SCCACHE_SHA256=aec995a83ad3dff3d14b6314e08858b7b73d35ca85a5bcf3d3a9ec07dee35
 ARG RUSTUP_INIT_VERSION=1.29.0
 ARG RUSTUP_INIT_TARGET=x86_64-unknown-linux-gnu
 ARG RUSTUP_INIT_SHA256=4acc9acc76d5079515b46346a485974457b5a79893cfb01112423c89aeb5aa10
-ARG RUST_TOOLCHAIN=nightly-2026-03-21
+ARG RUST_TOOLCHAIN=1.96.1
 
 ENV RUSTUP_HOME=/opt/rustup \
     CARGO_HOME=/opt/cargo \

.github/runner-scale-sets/query-regression/README.md

@@ -158,7 +158,7 @@ overridable via `QUERY_REGRESSION_RUNNER_UID`/`QUERY_REGRESSION_RUNNER_GID`)
 and exact tool versions: `libprotoc 3.21.12`, `uv 0.11.26`, `mold 2.40.4`,
 `Python 3.14.4`, `sccache 0.16.0`, `otelgen` commit
 `863a3f395d062c7322cc1de08a38774b7fdaa6c8`, root-owned `rustup 1.29.0`, and
-the image-baked `nightly-2026-03-21` Rust toolchain. `mold` and `python3`
+the image-baked `1.96.1` Rust toolchain. `mold` and `python3`
 come from apt at image-build time (not Ubuntu 24.04's default 3.12); bump
 the Verify pins together with `QUERY_REGRESSION_ECS_IMAGE_ID` when the
 image is rebuilt. Rustup, Cargo, and Rustc

.github/workflows/query-regression.yml

@@ -190,7 +190,7 @@ jobs:
       CARGO_HOME: /home/runner/.cargo
       UV_CACHE_DIR: /home/runner/.cargo/uv-cache
       RUSTUP_HOME: /opt/rustup
-      RUSTUP_TOOLCHAIN: nightly-2026-03-21
+      RUSTUP_TOOLCHAIN: 1.96.1
       RUSTUP_AUTO_INSTALL: "0"
       CARGO_TARGET_DIR: /home/runner/query-regression-target
       QUERY_REGRESSION_CACHE_META: /home/runner/query-regression-cache-meta
@@ -505,13 +505,13 @@ jobs:
           require_eq rustc_path "$(command -v rustc || true)" "/opt/cargo/bin/rustc"
           require_match rustup "$(capture rustup --version)" '^rustup[[:space:]]1\.29\.0([[:space:]]|$)'
           require_match cargo "$(capture cargo --version)" \
-            '^cargo[[:space:]]1\.96\.0-nightly[[:space:]]\(cbb9bb8bd[[:space:]][0-9]{4}-[0-9]{2}-[0-9]{2}\)$'
+            '^cargo[[:space:]]1\.96\.1[[:space:]]\(356927216[[:space:]][0-9]{4}-[0-9]{2}-[0-9]{2}\)$'
           require_match rustc "$(capture rustc --version)" \
-            '^rustc[[:space:]]1\.96\.0-nightly[[:space:]]\(ac7f9ec7d[[:space:]][0-9]{4}-[0-9]{2}-[0-9]{2}\)$'
+            '^rustc[[:space:]]1\.96\.1[[:space:]]\(31fca3adb[[:space:]][0-9]{4}-[0-9]{2}-[0-9]{2}\)$'
           require_match active_toolchain "$(capture rustup show active-toolchain)" \
-            '^nightly-2026-03-21-x86_64-unknown-linux-gnu([[:space:]]|$)'
+            '^1\.96\.1-x86_64-unknown-linux-gnu([[:space:]]|$)'
           require_eq RUSTUP_HOME "${RUSTUP_HOME}" "/opt/rustup"
-          require_eq RUSTUP_TOOLCHAIN "${RUSTUP_TOOLCHAIN}" "nightly-2026-03-21"
+          require_eq RUSTUP_TOOLCHAIN "${RUSTUP_TOOLCHAIN}" "1.96.1"
           require_eq RUSTUP_AUTO_INSTALL "${RUSTUP_AUTO_INSTALL}" "0"
           require "readable /opt/rustup" test -r /opt/rustup
           require "executable /opt/rustup" test -x /opt/rustup

AGENTS.md

@@ -25,7 +25,7 @@ provides sub-second querying at PB scale with high cost efficiency.
 | Lint | `make clippy` (= `cargo clippy --workspace --all-targets --all-features -- -D warnings`) |
 | Type check | `make check` |
 
-Toolchain: Rust nightly, Protobuf compiler (>= 3.15), C/C++ build essentials.
+Toolchain: Rust (stable, pinned by `rust-toolchain.toml`), Protobuf compiler (>= 3.15), C/C++ build essentials.
 Install the test runner with `cargo install cargo-nextest --locked`.
 
 ## Repo map

README.md

@@ -168,7 +168,7 @@ Read more in the [full Install Guide](https://docs.greptime.com/getting-started/
 ## Build From Source
 
 **Prerequisites:**
-* [Rust toolchain](https://www.rust-lang.org/tools/install) — nightly, pinned by [`rust-toolchain.toml`](https://github.com/GreptimeTeam/greptimedb/blob/main/rust-toolchain.toml)
+* [Rust toolchain](https://www.rust-lang.org/tools/install) — stable, pinned by [`rust-toolchain.toml`](https://github.com/GreptimeTeam/greptimedb/blob/main/rust-toolchain.toml)
 * [Protobuf compiler](https://grpc.io/docs/protoc-installation/) (>= 3.15)
 * C/C++ building essentials: `gcc` / `g++` / `autoconf` and the glibc dev package (`libc6-dev` on Ubuntu, `glibc-devel` on Fedora)
 * Python toolchain (optional, only for some test scripts)