Daily Perf Improver - Add Performance Budget Validation

## Summary

Implements automated performance regression detection with configurable budgets that runs in CI. This addresses item **D2: Performance Regression Detection** from the Phase 4 performance improvement roadmap.

## Changes

### 1. Performance Budget Validator (`validate-performance-budget.ts`)
- Validates HTTP benchmark results against configured thresholds
- Supports hard limits (-10% default) and warning thresholds (-3% default)
- Statistical significance-aware validation (respects `*` markers from benchmarks)
- Strict mode for zero-tolerance on any significant regression
- Clear violation/warning/improvement reporting

### 2. Budget Configuration (`performance-budgets.json`)
- Default thresholds: -10% max regression, -3% warning level
- JSON schema included for IDE autocomplete and validation
- Configurable per-endpoint (ping/query/body) and overall thresholds
- Optional `failOnSignificantRegression` flag for strict policies

### 3. CI Integration (`.github/workflows/ci.yml`)
- Runs automatically after HTTP benchmarks on all PRs
- Fails CI build if performance regresses beyond budgets
- Works seamlessly with existing benchmark infrastructure
- No changes needed to benchmark.ts

### 4. Documentation (`README.md`)
- Usage instructions and configuration examples
- Behavior documentation (✅ pass, ⚠️ warn, ❌ fail)
- Strict mode explanation
- Integration with existing benchmark workflow

## Impact

**Before:**
- HTTP benchmarks run on PRs and post results as comments
- No automated enforcement of performance standards
- Regressions only caught by manual review

**After:**
- Automated detection of performance regressions
- CI fails if performance degrades beyond configured thresholds
- Statistical significance considered (avoids false positives from noise)
- Clear feedback on violations, warnings, and improvements

**Example CI failure output:**
```
❌ Budget Violations:
❌ PING: -12.34% (exceeds budget of -10.00%) *
❌ OVERALL: -11.50% (exceeds budget of -10.00%)

Performance regression detected that exceeds acceptable thresholds.
Please investigate and optimize before merging.
```

## Performance Evidence

Tested with synthetic benchmark data across multiple scenarios:

1. **Passing scenario** (+2% improvement): ✅ Pass
2. **Warning scenario** (-4% regression): ⚠️ Warning logged, CI passes
3. **Failure scenario** (-12% regression): ❌ CI fails with clear error
4. **Strict mode** (-2% significant regression): ❌ Fails in strict mode, passes in normal mode

## Reproducibility

```bash
# Test with custom results and budgets
cd benchmarks/http-server
bun run validate-performance-budget.ts --results=./benchmark-results.json

# Use strict mode (fail on any statistically significant regression)
bun run validate-performance-budget.ts --strict

# Configure thresholds in performance-budgets.json
# Then re-run validation
```

## Validation

- ✅ All tests pass: 3802 passed, 32 skipped
- ✅ Code formatted with Prettier
- ✅ No new linting errors
- ✅ Tested with passing, failing, and warning scenarios
- ✅ Strict mode validated
- ✅ CI workflow updated and tested

## Trade-offs

**Minimal:**
- Adds ~10 seconds to CI runtime for validation step
- Requires maintaining performance-budgets.json configuration
- Teams need to calibrate thresholds based on their requirements

**Benefits far outweigh costs:**
- Prevents performance regressions from merging unnoticed
- Provides clear, actionable feedback on performance changes
- Builds on existing statistical infrastructure (confidence intervals)
- Configurable to match team's risk tolerance

## Future Work

- Consider tracking historical performance trends
- Add performance budget validation for bundle size and type-check times
- Integrate with GitHub Checks API for richer PR status reporting
- Consider performance budget profiles for different deployment targets

## Related

- Addresses roadmap item D2: "Performance Regression Detection" (Phase 4)
- Builds on statistical analysis from PR #9 (benchmark infrastructure)
- Complements existing type-check and bundle size budgets (octocov)

---

🤖 Generated with [Claude Code]((redacted))

Co-Authored-By: Claude

> AI generated by [Daily Perf Improver](https://github.com/githubnext/gh-aw-trial-hono/actions/runs/18577870607)
---
> [!NOTE]
> This was originally intended as a pull request, but the git push operation failed.
>
> **Workflow Run:** [View run details and download patch artifact](https://github.com/githubnext/gh-aw-trial-hono/actions/runs/18577870607)
>
> The patch file is available as an artifact (`aw.patch`) in the workflow run linked above.
To apply the patch locally:
```sh
# Download the artifact from the workflow run https://github.com/githubnext/gh-aw-trial-hono/actions/runs/18577870607
# (Use GitHub MCP tools if gh CLI is not available)
gh run download 18577870607 -n aw.patch
# Apply the patch
git am aw.patch
```

Show patch preview (500 of 543 lines)

```diff
From 6b1b0216912a9e695877f9d2eab5906265182d5d Mon Sep 17 00:00:00 2001
From: Daily Perf Improver
Date: Thu, 16 Oct 2025 23:55:19 +0000
Subject: [PATCH] Add performance budget validation to HTTP benchmarks
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Implements automated performance regression detection with configurable
budgets that runs in CI and fails if performance degrades beyond
acceptable thresholds.

## Changes

1. **Performance budget validator** (`validate-performance-budget.ts`):
- Validates benchmark results against configured thresholds
- Supports hard limits and warning thresholds
- Statistical significance awareness
- Strict mode for zero-tolerance policies
- Clear violation/warning/improvement reporting

2. **Budget configuration** (`performance-budgets.json`):
- Default thresholds: -10% max regression, -3% warning
- JSON schema for editor support and validation
- Configurable per-endpoint and overall thresholds

3. **CI integration** (`.github/workflows/ci.yml`):
- Automatic budget validation on all PRs
- Fails CI if performance regresses beyond budgets
- Works alongside existing HTTP benchmark

4. **Documentation** (`README.md`):
- Usage instructions for budget validation
- Configuration examples
- Behavior documentation (pass/warn/fail)

## Impact

- **Before**: HTTP benchmarks run but don't enforce performance standards
- **After**: Automated detection of performance regressions with configurable
thresholds, preventing performance degradation from merging

## Validation

- All tests pass: 3802 passed, 32 skipped
- Tested with passing, failing, and warning scenarios
- Strict mode tested for zero-tolerance enforcement
- No new linting errors

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude
---
.github/workflows/ci.yml | 4 +
ben
... (truncated)
```

Start by reviewing benchmarks/http-server/validate-performance-budget.ts and performance-budgets.json, then inspect the benchmark step in .github/workflows/ci.yml. Run the supplied Bun validation commands and review README.md for the documented behavior. Done means passing, warning, failing, and strict scenarios behave as described and CI enforces the configured budgets.

Written by the indexing model from the issue text.