refactor: simplify depthLimit in partial tags and tighten security docs

Drop try/finally around depthLimit in include, layout, and render; release at generator end. Consolidate production guidance in security-model.md. Fix padded-blocks lint in dos.spec.ts.

Co-authored-by: Cursor <[email protected]>

test/integration/liquid/dos.spec.ts

@@ -54,7 +54,6 @@ describe('DoS related', function () {
       await expect(liquid.parseAndRender('{% render "large" %}')).rejects.toThrow('template limit exceeded')
       await expect(liquid.parseAndRender('{% render "small" %}')).resolves.toBe('12345')
     })
-
   })
 
   describe('#outputLengthLimit', () => {