fix(build): Cargo.lock duplicate `capnp` entry breaks all build/prover CI (`package capnp specified twice`)

[hyperpolymath]

Symptom

Every build-dependent CI job fails at the build step with:

package `capnp` is specified twice in the lockfile
##[error]Process completed with exit code 101.

This reds all build/prover jobs at once — MVP Smoke, Boot Gate, and the entire T1/* live-prover matrix (z3, cvc5, vampire, spass, glpk, minizinc, eprover, alt-ergo, chuffed) — because each builds before doing anything else.

Root cause

Cargo.lock contains a duplicate capnp package entry. This lands with the capnpc 0.25.3 → 0.26.0 bump (#267, now on main): the lockfile update left two [[package]] name = "capnp" stanzas, which cargo rejects.

Scope

• Pre-existing on main — independent of any PR diff (observed on chore: add RSR git hooks + AFFIRMATION.adoc + 2026-06-15 handoff/status #271, a docs-only PR, whose own governance/doc gates all pass). It will red every build PR until fixed.
• Distinct from fix(ci): formal-verification creusot-verify cannot apt-install alt-ergo #250 (alt-ergo apt gap) — that T1/alt-ergo job now fails earlier, at this build step.

Fix

Regenerate / de-duplicate the lockfile, e.g. cargo update -p capnp (or --workspace), or hand-remove the duplicate stanza, then verify cargo build resolves. Needs a cargo environment to confirm; ship as a small dedicated PR off main.

Surfaced 2026-06-15 during estate maintenance (#238 follow-on).