fix: route all build outputs to builds/, fix S3 deploy MIME types

[Copilot]

Reports missing from docs/ after release because Playwright/test-results wrote to repo root instead of builds/. S3 deploy had incomplete MIME type coverage — JSON, XML, SVG, TXT, and webmanifest files either got wrong types or weren't uploaded at all.

Build output consolidation

All build artifacts now route through builds/:

Tool	Before	After
Vitest coverage	builds/coverage	(unchanged)
TypeDoc	builds/api	(unchanged)
Playwright HTML	playwright-report/	builds/playwright-report
JUnit XML	test-results/junit.xml	builds/test-results/junit.xml
Lighthouse	test-results/lighthouse-reports/	builds/test-results/lighthouse-reports/

• .gitignore: added playwright-report/ and test-results/ entries
• copy-test-reports.ts: updated source path, added warning log on missing source dirs (was silently swallowing ENOENT)

S3 deploy MIME type overhaul

Every text-based type now uses --no-guess-mime-type with explicit --content-type:

# Before: CSS without charset, JS with legacy type, SVG lumped with raster images,
#          JSON/XML only covered 4 named files, webmanifest not handled at all

# After: per-type sync commands
--content-type 'text/css; charset=utf-8'
--content-type 'text/javascript; charset=utf-8'
--content-type 'image/svg+xml'
--content-type 'application/json; charset=utf-8'
--content-type 'text/xml; charset=utf-8'
--content-type 'text/plain; charset=utf-8'
--content-type 'application/manifest+json'

Added builds/ and runbooks/ to the EXCL array to prevent deploying intermediate artifacts.

Workflow path updates

Updated artifact upload paths in e2e.yml, test-and-report.yml, slsa-provenance.yml, and .lighthouserc.json to match the new builds/ structure.

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