fix(imports): eliminate circular dependencies with type-fns

.agent/repo=.this/role=any/briefs/rule.forbid.barrel-imports-from-typefns.md

@@ -0,0 +1,35 @@
+# rule.forbid.barrel-imports-from-typefns
+
+## .what
+
+never import from `'type-fns'` barrel in this repo; always use scoped imports.
+
+## .why
+
+circular dependency hazard:
+
+```
+helpful-errors → type-fns (barrel)
+     ↑               ↓
+     │          re-exports withAssure
+     │               ↓
+     └───── withAssure imports HelpfulError
+```
+
+the type-fns barrel re-exports `withAssure`, which imports `HelpfulError` from this package. barrel import creates a circular dependency at runtime.
+
+## .pattern
+
+```ts
+// forbidden - barrel import triggers cycle
+import { isAFunction, isAPromise } from 'type-fns';
+
+// required - scoped imports avoid cycle
+import { isAFunction } from 'type-fns/dist/checks/isAFunction';
+import { isAPromise } from 'type-fns/dist/checks/isAPromise';
+import { omit } from 'type-fns/dist/companions/omit';
+```
+
+## .enforcement
+
+barrel import from type-fns = blocker

package.json

@@ -45,7 +45,8 @@
     "test:lint:deps": "npx depcheck -c ./.depcheckrc.yml",
     "test:lint:biome": "biome check --diagnostic-level=error",
     "test:lint:biome:all": "biome check",
-    "test:lint": "npm run test:lint:biome && npm run test:lint:deps",
+    "test:lint:imports": "dpdm --no-warning --no-tree --exit-code circular:1 --exclude '^$' 'src/**/*.ts'",
+    "test:lint": "npm run test:lint:biome && npm run test:lint:imports && npm run test:lint:deps",
     "test:unit": "set -eu && jest -c ./jest.unit.config.ts --forceExit --verbose --passWithNoTests $([ -n \"${CI:-}\" ] && echo '--ci') $([ -z \"${THOROUGH:-}\" ] && echo '--changedSince=main') $([ -n \"${RESNAP:-}\" ] && echo '--updateSnapshot')",
     "test:integration": "set -eu && jest -c ./jest.integration.config.ts --forceExit --verbose --passWithNoTests $([ -n \"${CI:-}\" ] && echo '--ci') $([ -z \"${THOROUGH:-}\" ] && echo '--changedSince=main') $([ -n \"${RESNAP:-}\" ] && echo '--updateSnapshot')",
     "test:acceptance:locally": "set -eu && npm run build && LOCALLY=true jest -c ./jest.acceptance.config.ts --forceExit --verbose --runInBand --passWithNoTests $([ -n \"${RESNAP:-}\" ] && echo '--updateSnapshot')",
@@ -65,7 +66,6 @@
   },
   "devDependencies": {
     "@biomejs/biome": "2.3.8",
-    "domain-objects": "0.31.7",
     "@commitlint/cli": "19.5.0",
     "@commitlint/config-conventional": "19.5.0",
     "@swc/core": "1.15.3",
@@ -82,6 +82,8 @@
     "declastruct": "1.7.3",
     "declastruct-github": "1.3.0",
     "depcheck": "1.4.3",
+    "domain-objects": "0.31.9",
+    "dpdm": "4.0.1",
     "esbuild-register": "3.6.0",
     "husky": "8.0.3",
     "jest": "30.2.0",