Design: Dependency-Fidelity — making "CI green" mean declared ≡ witnessed

[briansrls]

Adds docs/plans/dependency-fidelity-design.md — an operator-directed design doc (companion to the enforcement-intent thread) that makes "CI green" mean declared dependency structure ≡ witnessed (by-execution) structure.

Motivated by the int-literal keystone bug: an ingested fn body silently failed to become a substrate Arrow, passed CI green, and collected two diff-level APPROVEs while behaviorally dead — because the one witness that exercised the capability lived in a CI-excluded directory.

Contents (serially reasoned per DESIGN.md):

• §0 North star — change 5 lines → generate exactly the coverage needed, run only that.
• §2 The law — declared ≡ witnessed; fractal (the checker is subject to its own law).
• §3 Three-way ray-tracing — (input, function, output); strong typing is the scene geometry; unreached declared outputs flagged.
• §4 Coverage = mutation-adequate discrimination — minimal witness set killing every single-edit mutation; generatable, minimal, per-relationship.
• §5 Two fidelity rules — under-claim (missing authority; the int-literal class) + over-claim (false coupling; global graph-cut, not local).
• §6 Soundness corpus — load-bearing anti-false-positive golden corpus; the only way to silence a flag is to add a justified pattern.
• §7 The engine — affected-set × testgen mechanizes the north star.
• §8–10 — staging, self-witnessing acceptance, open sub-threads.

Diff is a single new planning doc — no code, .dag, shell, or hand-Rust changes.

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