dev: include Markdown link checks in the local lint suite

`dev/rust_lint.sh` now runs `ci/scripts/markdown_link_check.sh` as a
read-only step, after the workflow install check and before the Rust
documentation build. The runner loads `LYCHEE_VERSION` from
`ci/scripts/utils/tool_versions.sh` and installs that pinned version
when `lychee` is missing. An already installed `lychee` is used as is,
matching the runner's existing policy for other tools.

The checker becomes executable so the runner can invoke it directly, as
it does for every other registered script. Its body, configuration,
file selection, and the GitHub workflow are unchanged, and `--write`
never reaches the link check.

Partial progress on #21048.

Author: kumarUjjawal

ci/scripts/markdown_link_check.sh

@@ -22,7 +22,9 @@
 #
 # Note: The installed checking tools (e.g., taplo) are not guaranteed to match
 # the CI versions for simplicity, there might be some minor differences. Check
-# `.github/workflows` for the CI versions.
+# `.github/workflows` for the CI versions. When this script installs a missing
+# tool that has a pinned version in `ci/scripts/utils/tool_versions.sh`, it
+# installs that pinned version. An already installed tool is used as is.
 #
 #
 #
@@ -84,10 +86,15 @@ while [[ $# -gt 0 ]]; do
 done
 
 SCRIPT_NAME="$(basename "${BASH_SOURCE[0]}")"
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+
+# Load the tool versions shared with CI (for example, LYCHEE_VERSION).
+source "${SCRIPT_DIR}/../ci/scripts/utils/tool_versions.sh"
 
 ensure_tool "taplo" "cargo install taplo-cli --locked"
 ensure_tool "hawkeye" "cargo install hawkeye --locked"
 ensure_tool "typos" "cargo install typos-cli --locked"
+ensure_tool "lychee" "cargo install lychee --locked --version ${LYCHEE_VERSION}"
 
 run_step() {
   local name="$1"
@@ -107,6 +114,7 @@ declare -a WRITE_STEPS=(
 
 declare -a READONLY_STEPS=(
   "ci/scripts/check_no_cargo_install_in_workflows.sh|false"
+  "ci/scripts/markdown_link_check.sh|false"
   "ci/scripts/rust_docs.sh|false"
 )
 

dev/rust_lint.sh

@@ -188,7 +188,14 @@ tested in the same way using the [doc_comment] crate. See the end of
 
 ## Documentation Link Checks
 
-Run the internal markdown link check locally:
+The local lint suite, `./dev/rust_lint.sh`, includes the internal markdown link
+check. When `lychee` is not on your `PATH`, the suite installs the version
+pinned in `ci/scripts/utils/tool_versions.sh`, which is the version CI uses. An
+already installed `lychee` is used as is, so its version can differ from the
+CI pin. The check is read-only: `--write` and `--allow-dirty` do not change
+links.
+
+Run the internal markdown link check on its own:
 
 ```shell
 source ci/scripts/utils/tool_versions.sh