chore(repo): codify repo hygiene

[fdatoo]

Summary

• codify repo onboarding with AGENTS.md, CLAUDE symlink, EditorConfig, git hooks, and Taskfile checks
• add semantic config apply messages through CLI/API/MCP/events and generated protos
• move sample page/display fragments under examples and fix existing pkllsp lint failures

Validation

• pre-commit hook: fmt-check, golangci-lint, proto generation, Pkl config evaluation
• pre-push hook: go test ./..., go test -race ./..., go test -tags=integration ./...
• task fmt-check
• task proto:check
• task tidy:check
• task driverkit:tidy:check
• go test ./...
• go test -tags=integration ./...
• go test ./... in switchyard-driverkit
• golangci-lint run ./...
• golangci-lint run ./... in switchyard-driverkit
• npm test --prefix app
• npm run typecheck --prefix app
• npm run build --prefix app
• task build