Add SQL Server routine autocomplete

[Maxteabag]

Summary

• load SQL Server procedures, scalar functions, table-valued functions, and parameters from INFORMATION_SCHEMA
• suggest procedure parameters after EXEC/EXECUTE
• suggest scalar functions in expressions and TVFs after FROM, JOIN, and APPLY
• support schema/database qualification, bracketed identifiers, return-status assignments, later arguments, and semicolon-free batches
• keep rich autocomplete metadata separate from explorer name-only caches
• preserve legacy provider behavior and avoid ambiguous cross-schema/database parameter suggestions

Fixes #255.

Validation

• focused routine/adapter/completion suites: 118 passed
• real SQL Server instance verified procedure, scalar-function, TVF, return type, and parameter metadata
• Ruff and mypy: clean
• structured autoreview: clean after resolving cache, qualification, context, ambiguity, and API-contract edge cases