fatou

Add a new built-in lint rule to the fatou linter—implement it against the single-walk dispatch, register it in the one source of truth, add TDD behavior tests (plus autofix coverage when the rule ships a fix), and wire up the snapshot-pinned generated docs and the hand-maintained SUMMARY.md index.

Grow Fatou's Julia parser toward JuliaSyntax.jl using the differential oracle. The projector at src/parser/sexpr.rs walks the CST and emits JuliaSyntax's s-expression shape; the harness in tests/juliasyntax_oracle.rs diffs each fixture against pinned expected.sexpr. Use this skill to pick the next gap from the corpus, add the grammar plus projector support, lock it with a fixture, and ratchet the now-passing cases into the allowlists. The projector is a test-only diagnostic: a divergence means the CST (or the projector's encoding translation) is wrong, never patch it in the projector to make the test pass.

Grow Fatou's own Julia formatter, one construct at a time, against hand-authored fixtures. rules::lower (src/formatter/rules.rs) lowers the CST into the layout IR (ir.rs) printed by printer.rs; the gate in tests/formatter.rs diffs each fixture's format(input.jl) against a hand-written expected.jl. There is no external reference formatter: you propose a formatting, the user edits expected.jl to the desired form, you push back if it breaks a tenet or conflicts with an existing rule, then you implement the rule. Parser/lexer blockers stop and hand off to parser-parity.