fix(tests): skip Playwright tests when browser not installed (#77)

## Task
nanoclaw Coverage Floor fix — guard Playwright-dependent tests with
skipIf

## Owned files
- `src/__tests__/signer-integration.test.ts`
- `src/signer/__tests__/docusign-executor.test.ts`

## Problem
Both files call `chromium.launch()` in `beforeAll` hooks. When
Playwright
browsers aren't installed in the CI runner, the launch crashes, the 4
affected
tests fail, and `coverage-summary.json` is never written → Coverage
Floor CI
check has been red for 8+ days.

## Fix
Added `const hasPlaywright = fs.existsSync(chromium.executablePath())`
and
wrapped both top-level `describe` blocks with
`describe.skipIf(!hasPlaywright)`.
Tests still run locally and in any runner where `npx playwright install`
was run.

## Acceptance command + output
```
npx vitest run --reporter=verbose 2>&1 | tail -10
# (shows skipped instead of crashed when no browser installed)
```

## Coverage delta
Before: N/A (coverage-summary.json was never written — check was always
failing)
After: Coverage Floor CI check unblocked; tests skip gracefully

## Auto-merge rationale
Test-only change; no production code touched. Fixes a CI infrastructure
failure.

## Codex pre-review
skipped — sub-50-LOC trivial change

## HUMAN_READABLE_SUMMARY
Two Playwright-dependent test suites were crashing the CI coverage run
by calling
chromium.launch() in environments where browsers aren't installed. This
PR adds a
one-line existsSync guard and wraps both describe blocks with
describe.skipIf so
they skip gracefully instead of crashing. Coverage Floor CI will be
unblocked once merged.

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

Co-Authored-By: Claude <noreply@anthropic.com>

Co-authored-by: Claude <noreply@anthropic.com>

Author: topcoder1

src/__tests__/signer-integration.test.ts

@@ -16,6 +16,7 @@ import { docusignExecutor } from '../signer/docusign-executor.js';
 import { getCeremony } from '../signer/ceremony-repo.js';
 
 const FIXTURES = path.join(import.meta.dirname, '../signer/__tests__/fixtures');
+const hasPlaywright = fs.existsSync(chromium.executablePath());
 
 // Test executor extends docusignExecutor with localhost/127.0.0.1 in the whitelist
 const testDocusignExecutor = {
@@ -27,7 +28,7 @@ const testDocusignExecutor = {
   ],
 };
 
-describe('signer end-to-end integration', () => {
+describe.skipIf(!hasPlaywright)('signer end-to-end integration', () => {
   let browser: Browser;
   let server: http.Server;
   let port: number;

src/signer/__tests__/docusign-executor.test.ts

@@ -17,6 +17,7 @@ import { isWhitelistedUrl } from '../executor-registry.js';
 import type { SignCeremony, SignerProfile } from '../types.js';
 
 const FIXTURES = path.join(import.meta.dirname, 'fixtures');
+const hasPlaywright = fs.existsSync(chromium.executablePath());
 
 function makeCeremony(overrides: Partial<SignCeremony> = {}): SignCeremony {
   return {
@@ -49,7 +50,7 @@ const profile: SignerProfile = {
   updatedAt: Date.now(),
 };
 
-describe('docusignExecutor', () => {
+describe.skipIf(!hasPlaywright)('docusignExecutor', () => {
   let browser: Browser;
   let server: http.Server;
   let port: number;