nomograph/pipeline v5.4.0

Changed:
- rust-cli image: Rust toolchain floor 1.93 -> 1.94. Unblocks crates whose
  MSRV moved to 1.94 (immediate driver: wasmtime 46 in extension). The check
  job runs `cargo clippy -- -D warnings`; 1.93->1.94 clippy delta canaried
  clean on muxr + synthesist (0 new lints). Fail-closed gate: a stray lint
  can only stall a bump MR, never redden main.
- hygiene gate no longer forbids AGENTS.md -- the portable, committed
  agent-onboarding file (dunn.dev tracks it in cycle/, othala/). nomograph
  now matches that convention. .claude/ stays forbidden. Reaches
  direct-include consumers on a v5.4.0 bump (un-reds runes); bundle
  intra-catalog hygiene pins remain at v4.3.0 (deliberate gate baseline).