Refine coding standards and testing guidelines

- Updated coding rule descriptions for clarity and emphasis on readability, meaningful comments, and test verification.
- Adjusted thresholds for test coverage on business logic from 80% to 75%, aligning with the canonical reference in `cursor-meta.mdc`.
- Enhanced guidelines for handling skipped tests, emphasizing the need for investigation and classification.
- Introduced completeness audit requirements for research decomposition to ensure thoroughness in addressing problem dimensions.

.cursor/skills/research/steps/03_engine-investigation.md

@@ -97,6 +97,16 @@ When decomposing questions, you must explicitly define the **boundaries of the r
 
 **Common mistake**: User asks about "university classroom issues" but sources include policies targeting "K-12 students" — mismatched target populations will invalidate the entire research.
 
+#### Decomposition Completeness Audit (MANDATORY)
+
+After generating sub-questions, verify the decomposition covers all major dimensions of the problem — not just the ones that came to mind first.
+
+1. **Domain discovery search**: Search the web for "key factors when [problem domain]" / "what to consider when [problem domain]" (e.g., "key factors GPS-denied navigation", "what to consider when choosing an edge deployment strategy"). Extract dimensions that practitioners and domain experts consider important but are absent from the current sub-questions.
+2. **Run completeness probes**: Walk through each probe in `references/comparison-frameworks.md` → "Decomposition Completeness Probes" against the current sub-question list. For each probe, note whether it is covered, not applicable (state why), or missing.
+3. **Fill gaps**: Add sub-questions (with search query variants) for any uncovered area. Do this before proceeding to Step 2.
+
+Record the audit result in `00_question_decomposition.md` as a "Completeness Audit" section.
+
 **Save action**:
 1. Read all files from INPUT_DIR to ground the research in the project context
 2. Create working directory `RESEARCH_DIR/`
@@ -109,6 +119,7 @@ When decomposing questions, you must explicitly define the **boundaries of the r
    - List of decomposed sub-questions
    - **Chosen perspectives** (at least 3 from the Perspective Rotation table) with rationale
    - **Search query variants** for each sub-question (at least 3-5 per sub-question)
+   - **Completeness audit** (taxonomy cross-reference + domain discovery results)
 4. Write TodoWrite to track progress
 
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