chore(release): prepare v0.31.2 [release:v0.31.2]

[tcballard]

Summary

Prepares v0.31.2. It ships the glibc 2.17 floor for the Linux release archives (#511) and the dependency refresh: #473 rust-dependencies, #436 npm-dependencies, #448 github-actions, plus the source fixes in #512 that #473 and #436 needed.

Adds:

• Version 0.31.2 in rust/Cargo.toml, the =0.31.2 asdecided-core pins in decided and decided-mcp, and the 3-line Cargo.lock update (cargo update -w).
• server.json version and MCP image tag mcp-v0.31.2.
• docs/quickstart.md image tags v0.31.2.
• A dated ## v0.31.2 — 2026-10-05 CHANGELOG section with Fixed (the glibc floor) and Changed (the dependency refresh), keeping an empty ## Unreleased above it.

Scope

Included

• Version metadata and changelog only.

Excluded

• Tag and GitHub release. Publishing the release creates v0.31.2 and triggers native-publish.yml, which dispatches crates-publish.yml.

Verification

Ran

• scripts/verify-release-changelog.sh 0.31.2 reports changelog entry verified: v0.31.2.
• cargo test --workspace --release gives 524 passed and 0 failed. cargo fmt --all --check is clean and cargo clippy --release --no-deps -- -D warnings is clean.
• scripts/build-linux-release.sh x86_64-unknown-linux-gnu reports GLIBC_2.17 as the newest symbol for both binaries.
• scripts/smoke-linux-floor.sh in CentOS 7 prints ldd (GNU libc) 2.17 and decided 0.31.2; validate, relationships and gate pass, and decided-mcp: initialize ok.
• No 0.31.1 remains in the bumped files.

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