docs(project): record PR 5174 id in KB POC plan filename

Author: rschlaefli

project/2026-07-15-kb-poc-plan.md project/2026-07-15-pr-5174-kb-poc-plan.mdproject/2026-07-15-kb-poc-plan.md renamed to project/2026-07-15-pr-5174-kb-poc-plan.md

@@ -4,9 +4,9 @@ Caveman form. Junior-executable. Read whole plan before slice 1.
 
 ## Plan Identity
 
-- Plan: `project/2026-07-15-kb-poc-plan.md`
+- Plan: `project/2026-07-15-pr-5174-kb-poc-plan.md`
 - Branch: `kb-poc` (worktree `trees/kb-poc`), base + target: `v3` (@ `e05743901`)
-- PR: TBD (draft PR carries this plan first, then slices)
+- PR: [#5174](https://github.com/uzh-bf/klicker-uzh/pull/5174) (draft; carries this plan first, then slices)
 - History:
   - [PR #5078](https://github.com/uzh-bf/klicker-uzh/pull/5078) — full-scale KB control-plane prototype (`codex/kb-management-ui` → `v3-ai`). Too large for MVP. This POC supersedes it as the mergeable path. Reference only — do NOT cherry-pick wholesale.
   - Review of 5078: `project/2026-07-07_pr5078_kb_review.md` on the 5078 branch — catalog of its bugs/gaps. POC avoids them by design (see Decisions).