fix(ci): unbreak Agda type-check install + Justfile heal duplicate

Two pre-existing failures left red on main after #220 merged:

- agda-meta-checker.yml: `cabal install Agda-2.7.0.1` aborts on a warm
  ~/.cabal cache with "Path '.../bin/agda' already exists"; add
  --overwrite-policy=always so the install is idempotent. Until this lands
  the Agda meta-checker never actually runs in CI.
- contractile.just defined a `heal` recipe that collides with the root
  Justfile's `heal` across `import?`, so `just` aborts with a
  duplicate-recipe error — breaking every `just` call incl. MVP Smoke's
  `just mvp-env`. Drop the contractile copy; keep the richer root recipe
  (and contractile's heal-provers).

https://claude.ai/code/session_01UAqDQaMwpUqWHUSZekGZWv

Author: claude

.github/workflows/agda-meta-checker.yml

@@ -49,7 +49,10 @@ jobs:
       - name: Install Agda
         run: |
           cabal update
-          cabal install Agda-2.7.0.1
+          # --overwrite-policy=always: the cached ~/.cabal restore already
+          # carries the agda symlink, so a plain install aborts with
+          # "Path '.../bin/agda' already exists" on a warm cache.
+          cabal install Agda-2.7.0.1 --overwrite-policy=always
 
       - name: Install Agda standard library
         run: |

contractile.just

@@ -190,13 +190,10 @@ intend-list:
     @echo ''
     @echo 'Run `cat .machine_readable/contractiles/intend/Intentfile.a2ml` for the source of truth.'
 
-# ── HEAL (recovery shortcuts referenced by bust/dust recipes) ─────────
-
-heal:
-    @echo 'just heal: workspace healing entry point'
-    @cargo --version >/dev/null 2>&1 && echo '  rust toolchain OK' || echo '  rust toolchain MISSING'
-    @julia --version >/dev/null 2>&1 && echo '  julia OK' || echo '  julia MISSING — see juliaup'
-    @echo 'For prover binaries: just heal-provers'
+# ── HEAL-PROVERS (recovery shortcut referenced by bust/dust recipes) ──
+# NB: `heal` itself is defined in the root Justfile. Defining it here too
+# made `just` abort with a duplicate-recipe error across the `import?`,
+# which broke every `just` invocation (and thus MVP Smoke's `just mvp-env`).
 
 heal-provers:
     @echo 'heal-provers: install missing Tier-1 prover binaries'