fix: remove vestigial build.rs from elicit_proofs

build.rs did nothing useful — proofs are pre-generated and committed.
Moved the regeneration instructions into README.md instead.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: crumplecup

crates/elicit_proofs/README.md

@@ -2,4 +2,14 @@
 
 Formal verification proof harnesses for the elicitation ecosystem.
 
-Harnesses are generated at build time by `build.rs` from `VerifiedStateMachine::vsm_kani_proof()` (and future Creusot/Verus equivalents).
+Proof files are pre-generated by the `elicitation generate` CLI and committed to the repository.
+To regenerate after changing VSM source files:
+
+```text
+elicitation generate kani    --crate-path crates/elicit_server/src/archive/vsm \
+                              --out crates/elicit_proofs/src/kani/generated
+elicitation generate creusot --crate-path crates/elicit_server/src/archive/vsm \
+                              --out crates/elicit_proofs/src/creusot/generated
+elicitation generate verus   --crate-path crates/elicit_server/src/archive/vsm \
+                              --out crates/elicit_proofs/src/verus/generated
+```