feat: driver-owned SQL Server query templates

[debba]

Summary

• Opt into the optional get_table_query_template contract with capabilities.table_query_templates.
• Generate SELECT previews using TOP, schema qualification and bracket-escaped identifiers.
• Generate guarded UPDATE/DELETE previews; UPDATE uses unique host-editor :value_N placeholders.
• Keep template generation pure: no database connection and no statement execution.
• Preserve existing RPC contracts and min_runtime_version.

Dependencies and issue scope

Refs #26. Stacked on #30 (base: fix/26-preserve-explicit-row-limits); merge the pagination fix first, then retarget this PR to main if necessary.
Matching host change: TabularisDB/tabularis#818.
The complete Generate SQL fix requires the host extension and both plugin changes.

Validation

• 218 unit tests and 3 host-model conformance tests passed.
• 3 live SQL Server pagination tests passed, including generating a SELECT template and executing it with host pagination enabled.
• Added captured JSON-RPC fixture and updated the conformance capture script.
• cargo clippy --all-targets -- -D warnings
• cargo fmt --all -- --check

Registry rollout

See docs/query-templates.md. Tabularium administrators must register optional capabilities.table_query_templates before publishing so lenient manifest ingestion does not strip it. No registry DB migration, new endpoint or SDK change. No production registry configuration has been changed.