docs(refactor-log): scaffold Plan 9 input/output unification changelog

Empty section template plus the doc-update checklist that the
post-Plan-9 follow-up pass will work through (combined with the still-
pending Plan 8 items so docs are written once).

Spec: docs/superpowers/specs/2026-05-06-input-output-unification-design.md §10, R30.

docs/superpowers/refactor-logs/2026-05-06-input-output-unification.md

@@ -0,0 +1,101 @@
+# Refactor Changelog — Input/Output Unification + Presenter + Error Middleware + Public-Surface Cleanup
+
+**Started:** 2026-05-06
+**Spec:** [2026-05-06-input-output-unification-design.md](../specs/2026-05-06-input-output-unification-design.md)
+**Plan:** [2026-05-06-plan-9-io-unification.md](../plans/2026-05-06-plan-9-io-unification.md)
+**Branch:** feature/io-unification
+
+This document captures every architectural change made during Plan 9
+execution, organized by category. After the plan is merged, use the
+"Doc update checklist" at the bottom to update external docs in a
+single follow-up pass — combined with the still-pending Plan 8
+doc-update items so docs are written once for the post-Plan-9 state.
+
+---
+
+## 1. Files added
+
+(populated as work progresses)
+
+## 2. Files modified
+
+(populated as work progresses)
+
+## 3. Pattern changes (code-level)
+
+### 3.1 Use-case files — input + output schemas + runtime parse
+(populated when use cases are migrated)
+
+### 3.2 Controller files — presenter + unknown input + view return type
+(populated when controllers are migrated)
+
+### 3.3 tRPC integration — feature-scoped procedures, schema reuse from use cases
+(populated when routers are migrated)
+
+## 4. Error-middleware adoption
+
+(populated when defineErrorMiddleware is wired in core-shared and consumed by features)
+
+## 5. Public-API surface
+
+### 5.1 ./ui subpath added per feature
+(populated as features adopt the subpath)
+
+### 5.2 Feature root index.ts cleanup
+(populated as features clean up their root exports)
+
+## 6. Test additions
+
+### 6.1 R25 — output-validation tests (use case)
+(populated when use cases gain malformed-input "repo lied" tests)
+
+### 6.2 R26 — router error-mapping tests
+(populated when feature routers gain TRPCError-translation tests)
+
+### 6.3 R27/R28 — presenter shape tests
+(populated when controllers with non-identity presenters add view-shape assertions)
+
+## 7. Open issues / deferred decisions
+
+(populated as encountered)
+
+---
+
+## Doc update checklist (deferred — combined with paused Plan 8 doc pass)
+
+After Plan 9 lands, the still-pending Plan 8 doc-update items resume
+and now also pick up Plan 9 rules. Each item below covers BOTH plans'
+material so we touch every file once.
+
+- [ ] `CLAUDE.md` — Key Conventions: append schema-in-use-case rule, presenter rule, controller `unknown` input rule, `./ui` subpath rule, schema-export-from-root rule
+- [ ] `AGENTS.md` (root) — Per-Package Conventions: document `./ui` subpath, schema reachability from feature root, factory-bound use cases / controllers (carry-over from Plan 8)
+- [ ] `docs/guides/adding-a-feature.md` — restructure to use the Plan-9 use-case template (with input + output schemas + parse), the Plan-9 controller template (with presenter), and the new `procedures.ts` step (per-feature error map)
+- [ ] `docs/guides/tdd-workflow.md` — update mock decision tree + worked example to factory injection (Plan 8) + R25 output-validation test pattern (Plan 9) + R26 router-error-mapping test pattern (Plan 9)
+- [ ] `docs/guides/testing-strategy.md` — Mocking section: direct factory injection (Plan 8); R25/R26/R27/R28 test obligations (Plan 9)
+- [ ] `docs/architecture/vertical-feature-spec.md` — §6 file shape: schemas + presenter + procedures.ts; §10 testing: R25/R26/R27/R28
+- [ ] `docs/architecture/overview.md` — data-flow box: add input schema, output schema, presenter, error-middleware lanes
+- [ ] `docs/architecture/dependency-flow.md` — verify (no expected change beyond a `./ui` mention)
+- [ ] `docs/decisions/adr-012-lazar-conformance.md` — append note that input/output unification + presenter + error middleware land in ADR-013
+- [ ] `docs/decisions/adr-013-input-output-unification.md` — created in this plan's final task (Task 9); link from prior ADRs
+- [ ] Per-feature `AGENTS.md` (auth/blog/media/marketing-pages/navigation) — Plan 8 file paths + Plan 9 schema/presenter/procedures patterns
+- [ ] `packages/core-testing/AGENTS.md` — note R25/R26 test patterns
+- [ ] `packages/core-shared/AGENTS.md` — document `defineErrorMiddleware` and the `t` re-export
+- [ ] Plan 8 plan/spec — add a one-line annotation that some controller/router patterns shifted in Plan 9; link to this changelog
+
+---
+
+## Notes for the doc-update pass author
+
+When updating external docs, apply these substitutions globally:
+
+| Old reference | New reference |
+|---|---|
+| Use case takes `{ x }` directly typed | Use case takes `XInput` (`z.infer<typeof xInputSchema>`); schema lives in same file |
+| Use case returns `Promise<Entity>` | Use case returns `Promise<XOutput>` validated by `xOutputSchema.parse(...)` |
+| Controller imports `z` and defines local `inputSchema` | Controller imports `xInputSchema` from the use-case file |
+| Controller input typed `Partial<z.infer<...>>` | Controller input typed `unknown` |
+| Controller returns `Promise<Entity>` | Controller has `function presenter(value: XOutput)`; returns `Promise<ReturnType<typeof presenter>>` (or `Promise<void>` for void use cases) |
+| Router uses `publicProcedure` from `core-shared/trpc/init` | Router uses feature's `xProcedure` from `./procedures` |
+| Router redefines input schema as `z.object({...})` in `.input(...)` | Router uses `.input(xInputSchema)` imported from the use-case file |
+| Domain error reaches the wire as a generic `TRPCError({ code: "INTERNAL_SERVER_ERROR" })` | Domain error mapped to specific code by `defineErrorMiddleware` in `procedures.ts` |
+| Frontend imports `articleBySlugQuery` from `@repo/blog` | Frontend imports from `@repo/blog/ui` |