docs(index): refresh sphinx index

[hkimw]

Summary

• Add docs/index.rst links for the May 7 documentation refresh.
• Add hidden toctree entries for the new quickstart, spec, design, contributor, release-template, and news pages.

Dependencies

• Depends on the referenced page branches landing first: docs(spec): v002.1 architecture explainer #48, docs(spec): gemma 3n e4b path overview #50, docs(template): release notes template #51, docs(design): v002.1 decisions log #52, docs(contrib): contributors acknowledgements page #53, docs(quickstart): v002.1 reader path #54.
• Also references docs/news/README.md from docs/news-section-init, which does not currently have an open PR.

Verification

• git diff --check
• PATH="/tmp/pccx-idxref-wt/.venv/bin:/home/hwkim/.local/bin:/home/hwkim/bin:/home/hwkim/.codex/tmp/arg0/codex-arg0YM7pL1:/home/hwkim/.nvm/versions/node/v24.14.0/lib/node_modules/@openai/codex/node_modules/@openai/codex-linux-x64/vendor/x86_64-unknown-linux-musl/path:/home/hwkim/.local/bin:/home/hwkim/.local/bin:/home/hwkim/.local/bin:/home/hwkim/.nvm/versions/node/v24.14.0/bin:/tools/Xilinx/2025.2/Model_Composer/bin:/tools/Xilinx/2025.2/Vivado/bin:/tools/Xilinx/2025.2/PDM/bin:/tools/Xilinx/2025.2/Vitis/bin:/tools/Xilinx/2025.2/Vitis/bin:/tools/Xilinx/2025.2/Vitis/gnu/riscv/linux_toolchain/lin32/bin:/tools/Xilinx/2025.2/Vitis/gnu/riscv/linux_toolchain/lin64/bin:/tools/Xilinx/DocNav:/home/hwkim/.cargo/bin:/home/hwkim/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin:/snap/bin:/home/hwkim/.claude/plugins/cache/claude-plugins-official/rust-analyzer-lsp/1.0.0/bin:/home/hwkim/.claude/plugins/cache/claude-plugins-official/figma/2.1.30/bin" make strict (expected failure on this branch before dependencies land: missing toctree/doc references for the new pages)

[cloudflare-workers-and-pages]

Deploying pccx with    Cloudflare Pages

Latest commit:	43d67ae
Status:	✅  Deploy successful!
Preview URL:	https://e388714e.pccx.pages.dev
Branch Preview URL:	https://docs-index-refresh.pccx.pages.dev

View logs