[codex] Add wasm document preview reader

[phodal]

What changed

• Adds a debug Office WASM POC preview surface for DOCX, XLSX, and PPTX parsing/rendering.
• Adds the Routa-owned Office WASM reader bridge, protobuf encode/decode helpers, dependency pin checks, and protocol tests.
• Carries the workflow orchestrator singleton sync-load fix from the prior branch state.

Why

The previous branch history included verification screenshot PNGs under docs/issues/assets. This clean branch was rebuilt from origin/main with the same code changes but without screenshot files or screenshot markdown references.

Validation

• git rev-list --objects origin/main..HEAD | rg -i '.(png|jpe?g|gif|webp|svg|avif)$|office-wasm-poc/.*.png' -> no matches
• git log --all-match --regexp-ignore-case --grep='screenshot' --oneline origin/main..HEAD -> no matches
• git diff --check origin/main..HEAD
• npm run check:office-wasm-reader:deps
• npx vitest run src/client/office-document-viewer/protocol/tests/office-artifact-protobuf.test.ts src/client/office-document-viewer/protocol/tests/routa-office-wasm-reader.test.ts
• entrix run --tier fast

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Run ID: 976de640-117b-4cca-a0dc-be69bdc4e292

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch codex/office-wasm-poc-renderer-clean

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