config: Allow both user-managed and repo-managed configs per repo #6227

Job	Run time
check (protos)	2m 32s
build (no git)	1m 31s
test (macos-aarch64)	6m 45s
test (macos-x86_64)	14m 22s
test (windows-aarch64)	17m 51s
test (linux-x86_64-gnu)	6m 21s
check (codespell)	10s
check (rustfmt)	22s
test (linux-aarch64-gnu)	5m 3s
test (windows-x86_64)	16m 3s
check (cargo-deny, advisories)	23s
check (cargo-deny, sources)	22s
check (cargo-deny, bans)	24s
check (mkdocs)	15s
check (zizmor)	22s
check (doctests)	3m 5s
nix flake (ubuntu-24.04)	7m 48s
check (clippy)	1m 29s
check (Cargo.lock dependency count)	3s
check (cargo-deny, licenses)	24s
check (latest mkdocs, optional)	14s
nix flake (ubuntu-24.04-arm)	7m 21s
nix flake (macos-14)	9m 14s
required checks (merge queue)	0s
	1h 42m 24s

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