Align Dependabot coverage and add the dev-fast build fragment

.github/dependabot.yml

@@ -28,3 +28,10 @@ updates:
     cooldown:
       default-days: 7
       semver-major-days: 14
+  - package-ecosystem: rust-toolchain
+    directory: /
+    labels:
+      - dependencies
+      - rust-toolchain
+    schedule:
+      interval: weekly

AGENTS.md

@@ -380,3 +380,12 @@ The following tooling is available in this environment:
 
 These practices help maintain a high-quality codebase and facilitate
 collaboration.
+
+## Fast development builds
+
+`make dev-build` and `make dev-test` compile with the opt-in Cranelift
+backend and the mold linker configured in `tools/dev-fast/config.toml`.
+They require a nightly toolchain and, on Linux, a `mold` binary on the
+`PATH`. The fragment is passed explicitly with `--config`, so release,
+coverage, and verification builds are unaffected; never copy its contents
+into `.cargo/config.toml`, which Cargo applies to every build.

Makefile

@@ -105,3 +105,14 @@ rust-audit: ## Audit the Rust workspace for known vulnerabilities
 help: ## Show available targets
 	@grep -E '^[a-zA-Z_-]+:.*?##' $(MAKEFILE_LIST) | \
 	awk 'BEGIN {FS=":"; printf "Available targets:\n"} {printf "  %-20s %s\n", $$1, $$2}'
+
+# Opt-in accelerated debug builds (Cranelift + mold); requires a nightly
+# toolchain. See AGENTS.md and tools/dev-fast/config.toml.
+DEV_FAST_CONFIG ?= tools/dev-fast/config.toml
+
+.PHONY: dev-build dev-test
+dev-build: ## Build debug binaries with Cranelift and mold
+	cargo --config "$(DEV_FAST_CONFIG)" build
+
+dev-test: ## Run tests with Cranelift and mold
+	cargo --config "$(DEV_FAST_CONFIG)" test

tools/dev-fast/config.toml

@@ -0,0 +1,31 @@
+# Canonical opt-in Cargo configuration fragment for accelerated local debug
+# builds.
+#
+# This configuration is deliberately kept out of `.cargo/config.toml`.
+# Cargo auto-discovers that path, so anything placed there applies to
+# release packaging, coverage, and verification builds, which must keep
+# the supported LLVM backend and platform linker. In a consuming
+# repository this fragment lives at `tools/dev-fast/config.toml` and is
+# passed explicitly with `cargo --config tools/dev-fast/config.toml ...`
+# from `make dev-build` and `make dev-test`.
+#
+# Repositories that set repository-wide `rustflags` in `.cargo/config.toml`
+# must restate them in the target table below. Cargo joins the rustflags of
+# every matching `[target.*]` entry (target-triple and `cfg` tables alike),
+# but the joined target rustflags take precedence over `[build].rustflags`
+# rather than merging with it.
+
+[unstable]
+codegen-backend = true
+
+# Cranelift trades runtime performance for compile speed, so it applies to
+# the dev profile only. The `make dev-*` targets never build release
+# artefacts.
+[profile.dev]
+codegen-backend = "cranelift"
+
+# mold ships for Linux only, so the flag is gated behind a target `cfg`. On
+# macOS and Windows the table simply does not apply and the platform default
+# linker is used.
+[target.'cfg(target_os = "linux")']
+rustflags = ["-Clink-arg=-fuse-ld=mold"]

typos.local.toml

@@ -12,6 +12,13 @@ accepted = []
 
 [patterns]
 ignore = [
+  # "mold" names the linker (https://github.com/rui314/mold) in these
+  # contexts only; the mould correction stays active elsewhere.
+  "-fuse-ld=mold",
+  "mold linker",
+  "Cranelift \\+ mold",
+  "Cranelift and mold",
+  "`mold`",
   # Official documentation name.
   'Azure Architecture\s+Center\s+\|\s+Microsoft Learn',
   # Public design identifiers are exact API names.

typos.toml

@@ -38,9 +38,14 @@ extend-ignore-re = [
     "(?m)^### HookArtifact and HookSubscription$",
     "(?m)^use tokio::runtime::RuntimeFlavor;$",
     "(?s)```.*?```",
+    "-fuse-ld=mold",
     "Azure Architecture\\s+Center\\s+\\|\\s+Microsoft Learn",
+    "Cranelift \\+ mold",
+    "Cranelift and mold",
     "\\brust-analyzer\\b",
     "`[^`\\n]+`",
+    "`mold`",
+    "mold linker",
 ]
 
 [default.extend-words]