Sync engineering voice from canon; split repo conventions

[moskovich]

Why

The engineering voice in 05-engineering-voice.mdc was a hand-maintained paraphrase that had drifted from the canonical source. It was missing the current canon sections (truth discipline, compression tics, protocol-object naming) and was one of five inconsistent copies across repos.

What

• 05-engineering-voice.mdc is now a generated vendor of the single source of truth: feral-file/canon → reference/voice/engineering.md. It carries a do-not-edit banner. Regenerate with make sync-voice in canon after editing the source.
• 06-cli-conventions.mdc (new, hand-owned) keeps the genuinely ff-cli-specific parts that were mixed into the old file: Go-doc commenting standard, repo terminology, and CLI output rules. These are not brand voice, so they live in the repo layer, not the synced file.

Canon is private and this repo is public, so we vendor a generated copy rather than submodule canon. This is the model for the other repos with stale voice copies (ff-app, ff-exhibition, ff-source-resolver, feralfile-app).

[feralfile-bot]

Reviewers: 1 (approve: 0, comment: 1, request-changes: 0).

Optional cleanup:

• .cursor/rules/06-cli-conventions.mdc:10 says the file explains how the voice applies to “Go code,” but this repo is Node.js/TypeScript-first and the actual rule is Go-style documentation comments. Please reword that phrase so future agents do not infer that this repo contains or expects Go runtime code.

[moskovich]

Closing — we're keeping the engineering voice internal to canon and deleting the scattered repo copies rather than vendoring/syncing them. No per-repo voice file.