Redesign snapshot restoration for agents

[vigoo]

Summary

• Execute load-snapshot as a specially supported read-only lifecycle operation using the existing read_only_method: Some("load-snapshot") path, with no oplog writes and with mutating host operations plus outgoing HTTP/RPC rejected before they take effect.
• Replace mutation-based snapshot loaders with restoration factories across the Rust, TypeScript, Scala, and MoonBit SDKs. Restoration skips normal initialization, receives identity/principal/config context as supported by each SDK, and installs only a complete successfully restored state or instance.
• Generate automatic loading only where a JSON-deserialization contract exists, including requiring an explicit TypeScript state schema, while preserving the existing snapshot envelope, MIME, and WIT contracts.
• Make failed automatic loads discard partial state and recreate/replay without trying older automatic snapshots; preserve the previous component for failed manual updates.
• Migrate in-tree consumers and templates, add executor and SDK regression coverage, and update source and generated documentation.

Validation

• cargo fmt -p golem-worker-executor -- --check
• cargo clippy -p golem-worker-executor --all-targets --no-deps -- -D warnings
• cargo check -p golem-worker-executor --all-targets
• Targeted worker-executor snapshot/update acceptance tests: 4 passed
• Rust SDK tests: 132 passed, 4 ignored
• TypeScript SDK tests: 17 passed
• Scala formatting and model JVM/JS, macro, and core tests: 1,346 passed
• MoonBit SDK tests: 259 passed; SDK tools tests: 304 passed
• Migrated snapshot fixtures built successfully
• Docs lint, formatting, typecheck, links, version checks, and cargo make check-docs-skills

Resolves GOL-487

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