Simplify prompt testing + add Opus correctness reviewer (#11)

## Summary

Two changes in one PR:

### 1. Simplify the testing framework (-5,691 lines, +301 lines)

Removes the complex evaluation system:
- Claude-as-judge abstract scoring (5 numeric dimensions)
- Flask web review UI with localStorage persistence
- Human review JSONL collection system
- Prompt advisor / improvement suggestion engine
- 11 historical prompt YAML files
- Flask and Jinja2 dependencies

Keeps:
- All 21 curated test cases with real assembly
- CE API client and enrichment
- Core runner + CLI (both dramatically simplified)

### 2. Add focused Opus correctness reviewer (+258 lines)

Instead of abstract scores, uses Claude Opus to check for **specific
factual errors**:
- Instruction semantics (is `lea` correctly described?)
- Complexity claims (O(2^n) vs O(n)?)
- Optimisation level characterisation
- Register usage and calling conventions

Each issue is classified as **error** (would mislead a student) or
**warning** (imprecise but not wrong).

```bash
# Run + review in one step
uv run prompt-test run --review

# Review existing results
uv run prompt-test review results/file.json
```

### 3. Bump max_tokens from 1024 to 1536

Two test cases (`edge_long_asm_001` and `loop_experienced_assembly`)
were hitting the 1024 output token limit and getting truncated
mid-explanation. 1536 gives enough headroom for complex assembly without
encouraging verbosity. Cost impact is minimal since `max_tokens` is a
cap — most responses use 400-600 tokens.

### Why this approach

The old abstract scoring (accuracy: 0.67, relevance: 0.82...) didn't
catch real errors like the O(2^n)→O(n) fibonacci mistake. The new
reviewer asks specific questions about correctness and reports concrete
issues.

### Testing
- 91 unit tests pass
- Pre-commit clean
- Full 21-case run with Opus review: 20/21 passed correctness check

*(I'm Molty, an AI assistant acting on behalf of @mattgodbolt)*

Author: mattgodbolt

app/prompt.yaml

@@ -2,7 +2,7 @@ name: Production Sonnet 4.6
 description: Sonnet 4.6 with deduplicated, tighter prompts
 model:
   name: claude-sonnet-4-6
-  max_tokens: 1024
+  max_tokens: 1536
   temperature: 0.0
 audience_levels:
   beginner: