Two presentation refinements to the `aura graph` views, render-only (no
engine change, C8/C9/C23 untouched).
Edge colouring: thread a `Color { Plain, Ansi }` through render_flat /
render_definition / render_blueprint / render_compilat. `Ansi` uses
ascii-dag's colored scanline pass (per-edge palette colours) so crossing
edges stay traceable; `Plain` is the existing monochrome `g.render()`.
The CLI selects `Ansi` only when stdout is a TTY (`IsTerminal`), so a
redirect to a file or pipe stays byte-clean — `aura graph | …` carries no
escape codes. ascii-dag colours only edges; node-label text is unaffected.
Tests render `Color::Plain` explicitly, so both goldens stay byte-stable
(compiled_view_golden remains the C23 guard); a new test pins that `Ansi`
emits escapes and `Plain` does not, and that labels survive colouring.
Blank line: render_definition now separates the typed signature title from
the graph body with an empty line. blueprint_view_golden re-captured.
Considered but rejected this round: per-node role highlighting of the
signature identifiers — needs either an ascii-dag fork (node colouring is
hard-disabled upstream) or a per-graph string-surgery pass that does not
generalise beyond hand-known labels. Only edge colouring survives here.
Brummel
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