Add Domstack service worker example

[bcomnes]

Summary

Adds the handwritten static-MPA service-worker example on top of the core manifest and service-worker build APIs in #262.

• Implements precache, runtime-cache, navigation fallback, lifecycle, update, reset, inspection, and background-event flows without Workbox.
• Demonstrates layout/page manifest policy defaults through manifestVars and manifestBuilt.
• Includes example documentation and the standard service-worker design plan.

Validation

• npm run build --workspace=@domstack/static-mpa-offline-example
• npx tsc -p examples/static-mpa-offline/tsconfig.json

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[coveralls]

Coverage Report for CI Build 30649072370

Coverage increased (+0.6%) to 93.145%

Details

• Coverage increased (+0.6%) from the base build.
• Patch coverage: No coverable lines changed in this PR.
• No coverage regressions found.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

No coverage regressions found.

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Coverage Stats

Relevant Lines:	6087
Covered Lines:	5800
Line Coverage:	95.29%
Relevant Branches:	1105
Covered Branches:	899
Branch Coverage:	81.36%
Branches in Coverage %:	Yes
Coverage Strength:	163.62 hits per line

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💛 - Coveralls