[Ayinkx]

Makes the repository appeal-ready.

CI and security

• Raise MSRV from 1.85 to 1.88; stellar-xdr 28 -> serde_with -> darling 0.24.1 requires it.
• Replace serde_yml with serde_yaml_ng; removes
  oyalib and RUSTSEC-2026-0333.
• Update the MSRV CI job.

Metadata and docs

• Point repository, installation, and Wave links at AyinkxLab/stellar-contract-platform (the old StellarFoundry URLs redirect but were inconsistent).
• Update test count (147) and open-issue count (123).
• Add docs/WHY_OBSERVATORY.md positioning against �i-code-assistant, stellar-devkit, and soroban-security-scanner.
• Add a tag-driven release workflow for Linux x86_64, macOS arm64, and Windows x86_64 archives with SHA256 checksums.

Backlog

• Close feat(diff): add a Markdown renderer #9 (Markdown renderer), docs(config): document configuration precedence #102 (configuration precedence docs), docs(events): document the event JSON schema #112 (event schema docs) as completed.
• Rebuild the 20-issue Wave board with docs: add architecture decision records #110, docs(api): document the API version deprecation policy #127, and feat(rpc): bound RPC response sizes #119 replacing the completed issues.

Verification

• cargo +1.88.0 build --workspace --locked
• cargo +1.88.0 test --workspace --all-features --locked (147 tests)
• cargo fmt --all -- --check
• cargo clippy --workspace --all-targets --all-features -- -D warnings
• cargo audit --file Cargo.lock (0 vulnerabilities; one allowed unmaintained warning for unsafe-libyaml)