fix(postproduction): keep MSAA when postproduction is enabled

[rihokirss]

Description

Fixes #793.

Postproduction.initialize() creates the EffectComposer without a render target, so three.js allocates the ping-pong targets with samples = 0. The moment postproduction is enabled, the hardware MSAA of the default framebuffer is gone and every geometry edge is aliased; SMAA only partly recovers it, which is why the postproduction image looks "noisier" than the plain render.

This PR gives the composer targets a sample count:

• new Postproduction.samples (default 4, clamped to renderer.capabilities.maxSamples; 0 restores the previous behaviour), applied right after the composer is created and re-applied by the setter (samples change + dispose(), so the framebuffer is re-created on next use);
• setSize() needs no change — WebGLRenderTarget.setSize() keeps samples;
• the PostproductionRenderer example gets an "MSAA samples" slider next to the SMAA checkbox.

Measured on an office-building model, fixed exterior view, Chrome / AMD Radeon 8060S, 1665×1123 ("hard edges" = share of neighbouring pixel pairs whose luma differs by more than 60):

	hard edges	render ms
postproduction on, samples = 0 (before)	43.5 %	12.2
postproduction on, samples = 4 (this PR)	33.7 %	12.8
postproduction off (default framebuffer, MSAA)	36.2 %	9.9
postproduction on, samples = 0, pixel ratio 2	33.6 %	13.2

i.e. the same edge quality as pixel ratio 2 for ~0.6 ms per frame instead of 4× the fill rate.

Additional context

• The composer targets carry no depthTexture; the AO / edge-detection passes keep their own single-sample targets, so nothing else changes.
• yarn build-libraries currently fails on main in packages/core against the published @thatopen/fragments@3.4.7 (FragmentsModels.getWorker, getLocalIdsFromItemIds are not released yet) — unrelated to this change; tsc for packages/front reports no errors in PostproductionRenderer, and the front Vite build succeeds.
• The pre-existing eslint/prettier findings in the two touched files (import order, fragPaths line, extraneous-deps in the example) are left as they are to keep the diff minimal.

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

Before submitting the PR, please make sure you do the following:

• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• Follow the Conventional Commits v1.0.0 standard for PR naming.
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (fixes #793).
• Ideally, include relevant tests that fail without this PR but pass with it. (No test harness in this repo; the example exposes the setting.)