Align Dependabot coverage and add the dev-fast build fragment

.github/dependabot.yml

@@ -52,3 +52,10 @@ updates:
     cooldown:
       default-days: 7
       semver-major-days: 14
+  - package-ecosystem: rust-toolchain
+    directory: /
+    labels:
+      - dependencies
+      - rust-toolchain
+    schedule:
+      interval: weekly

AGENTS.md

@@ -457,3 +457,12 @@ 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.

typos.local.toml

@@ -9,6 +9,9 @@ stems = []
 accepted = []
 
 [words.corrections]
+# "mold" names the linker (https://github.com/rui314/mold); it is not a
+# misspelling of "mould" in that context.
+mold = "mold"
 
 [patterns]
 # The tokenizer splits the valid hyphenated prefix in `mis-grouping`.

typos.toml

@@ -1502,6 +1502,7 @@ extend-ignore-re = [
 "modularizers" = "modularizers"
 "modularizes" = "modularizes"
 "modularizing" = "modularizing"
+"mold" = "mold"
 "monetisable" = "monetizable"
 "monetisably" = "monetizably"
 "monetisation" = "monetization"