docs: align agent instructions and README guidance (#323)

.github/skills/README.md

@@ -13,7 +13,7 @@ Use one governance source to avoid duplicated or conflicting policy text.
 
 ## Skills
 
-- `medassist-karpathy-core` — enforce assumption clarity, simplicity, surgical diffs, and verifiable execution.
+- `medassist-karpathy-core` — enforce think-before-coding, simplicity-first changes, surgical diffs, and goal-driven verification.
 - `medassist-architecture-guard` — enforce frontend/backend boundary and `/api/*` data-flow conventions.
 - `medassist-db-compat-check` — enforce backward-compatible SQLite/Drizzle schema changes.
 - `medassist-i18n-enforcer` — enforce translation-key-only UI copy with EN/DE parity.

.github/skills/medassist-karpathy-core/SKILL.md

@@ -0,0 +1,69 @@
+---
+name: medassist-karpathy-core
+description: Apply assumption clarity, simplicity-first implementation, surgical diffs, and goal-driven verification for non-trivial coding tasks.
+---
+
+# Skill Instructions
+
+Use this skill as an execution style layer for implementation tasks where overengineering, broad refactors, or unclear assumptions are likely.
+
+## Use When
+
+- The request is ambiguous and assumptions must be made explicit.
+- The change can easily balloon in scope.
+- A bug fix or feature needs explicit success criteria and verification.
+- You need to keep diffs minimal and directly tied to the request.
+
+## Do Not Use When
+
+- The task is trivial and can be completed safely without extra process overhead.
+- The task is only about ownership routing (use `medassist-testing-handoff` / `medassist-release-handoff`).
+- The task is only about domain guardrails already covered by specialized skills (architecture, DB, i18n, UI, security, config, observability).
+
+## Core Principles
+
+### 1. Think Before Coding
+
+- Do not assume silently.
+- State assumptions explicitly.
+- If multiple interpretations exist, present them instead of picking one invisibly.
+- If uncertain or blocked by ambiguity, stop and ask.
+- If a simpler approach exists, call it out.
+
+### 2. Simplicity First
+
+- Implement the minimum code required to solve the asked problem.
+- Do not add speculative features, abstractions, or configurability.
+- Avoid defensive handling for impossible scenarios.
+- If the solution feels overcomplicated, simplify before finalizing.
+
+### 3. Surgical Changes
+
+- Touch only lines required for the request.
+- Do not refactor unrelated areas.
+- Match existing local style and patterns.
+- Remove only unused code introduced by your own change.
+- If unrelated dead code is discovered, mention it but do not remove it unless requested.
+
+### 4. Goal-Driven Execution
+
+- Translate requests into verifiable outcomes before implementation.
+- For multi-step tasks, define short steps with checks.
+- Verify the requested behavior explicitly before declaring done.
+
+Example execution frame:
+
+```text
+1. [Step] -> verify: [check]
+2. [Step] -> verify: [check]
+3. [Step] -> verify: [check]
+```
+
+## Response Format
+
+When this skill is used, report briefly:
+
+- Assumptions made (or clarifications requested)
+- Why the chosen approach is the simplest viable one
+- What was changed (and what was intentionally not changed)
+- Verification performed and result