docs(renderers): clarify optional renderer setup for Full packages

[p4535992]

Summary

• Clarify that optional specialist renderers are not automatically included in the historical @file-viewer/*-full packages or the frozen preset-all compatibility matrix.
• Add a generic installation and registration pattern that can be reused for current and future optional renderers.
• Document how to extend an existing Full installation with an optional renderer using rendererMode: 'extend', with DICOM as a concrete example.
• Clarify the CLI workflow and the difference between historical Full packages, the CLI full profile, and the prebuilt web-full browser bundle.

Related issue

N/A: documentation clarification only; no existing issue is being closed.

Change classification

• User-visible UI or rendering change
• Non-visual change
• File-format or renderer behavior
• Public API, package, Worker, WASM, or deployment-path change

Verification

Check	Result
Documentation/content review of docs/guide/on-demand-renderers.md	Pass
Runtime/build tests	N/A — documentation-only change

Sample / fixture evidence

• N/A: no file-format or renderer behavior is changed.

Visual evidence

• Before: N/A — documentation-only change.
• After: N/A — documentation-only change.

Risk and compatibility

• Affected packages/formats: Documentation for optional renderers and historical @file-viewer/*-full integrations. No package or format implementation is changed.
• Compatibility or migration risk: None expected. This documents the existing opt-in renderer behavior and does not change runtime, API, package, Worker, WASM, asset, or deployment behavior.
• Rollback: Revert the documentation commits.

Checklist

• I added or updated focused automated coverage, or explained why it is not needed.
• I updated user-facing documentation or release notes when behavior or API changed, or marked them not applicable.
• I verified offline/private-deployment paths when changing Worker, WASM, fonts, vendor assets, or URLs.
• I did not commit secrets, customer files, private samples, generated caches, or unrelated changes.

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-08-29T08:51:23.077667Z	c14a9ed	PR opened

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