sdks/ts: replace any with proper types in SDK core

[Myestery]

Summary

• Replace any types with unknown, generics, and proper type constraints across ~15 SDK files
• Use Reflect.construct for safe class instantiation in the decorator
• Use Object.assign pattern for typed function objects in client generation
• Add generic wrappers for deserialize/deserializeDataValue to maintain public API types while using unknown internally
• Extract MethodKeys<T> helper type for cleaner Client<T> definition
• Add MutableAgentStatics type to avoid (ctor as any).get = ... pattern

Context

Split from #2845 based on reviewer feedback. This PR focuses only on SDK type improvements, excluding:

• Bug fixes (see sdks/ts: fix serializer bugs and agentError null crash #2855)
• Metadata types (see sdks/ts: add MetadataJSON types to metadata pipeline #2856)
• REPL, ESLint config, lock file, and ts_bridge changes (dropped per reviewer request)

Test plan

• tsc --noEmit passes
• All 163 tests pass across 11 test files
• Rollup build succeeds

[github-actions]

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