Vendors v1's macro tree (34 files) into crates/dbt-loader/src/dbt_macro_assets/dbt-sqlserver,
mirroring dbt-fabric's directory layout rather than v1's, per the porting guide's
delegate-to-fabric-where-behavior-matches instruction.

Non-mechanical decisions, each checked against the v1 source, the shared
dbt-adapters package, or the Rust adapter_impl.rs added in Part 7:

- No sqlserver__generate_schema_name override: v2 has no per-adapter behavior-flag
  mechanism (Part 7 registered none for SqlServer), so the macro falls through to
  the shared default__generate_schema_name (standard target.schema_custom
  concatenation) rather than hardcoding v1's current no-prefix default. This is
  what dbt-msft/dbt-sqlserver#800 (filed last session) already assumes.
- adapter_specific_behavior_flags() being empty also means
  adapter.behavior.dbt_sqlserver_use_dbt_transactions doesn't exist in v2.
  hooks.sql's two branches on that flag emit identical SQL either way, so the
  conditional was dropped rather than left referencing an undefined attribute.
- full_refresh_build=prebuilt and table_refresh_method=dml (table.sql,
  incremental.sql) raise a compiler error instead of running: both depend on
  macros this PR doesn't port (create_table_as_prebuilt, table_dml_refresh),
  matching the loud-failure precedent set for custom indexes in Part 7's plan.
- sqlserver__get_create_index_sql raises a compiler error naming the config
  option, rather than inheriting the shared default's silent no-op — a model
  with indexes: configured would otherwise build successfully with none.
- Dropped everything gated on adapter.resolve_masks/apply_masks (table.sql,
  incremental.sql, snapshot.sql) and reconcile_indexes on persisted tables:
  neither has a v2 Rust counterpart, and since indexes: is already rejected
  loudly on first create, an already-existing table can't have a nonempty
  config to reconcile.
- Skipped unit_test_create_table_as.sql and its check_for_nested_cte helper:
  v2's tests/unit.sql materialization dispatches through the same
  get_create_table_as_sql used by every other build path, not a separate
  unit_test_create_table_as macro — the v1 file is unreachable in v2's call graph.
- Skipped materializations/models/view/create_view_as.sql
  (sqlserver__create_view_exec): grepped v1's own tree and found no caller;
  dead code inherited from an earlier Fabric-derived layout.
- Ported adapters/catalog.sql, matching dbt-fabric/macros/adapters/catalog.sql
  still being live in v2 for `dbt docs generate` — the Part 5 Rust metadata
  module doesn't replace it. v1's version is kept over Fabric's: it fills
  table_comment/column_comment from sys.extended_properties, consistent with
  porting the full persist_docs.sql (which Fabric punts on entirely).
- build_model_constraints(target_relation) added to table.sql and the
  full-refresh branch of incremental.sql (v1 doesn't call it, Fabric's newer
  materializations do) — v1's Python framework invoked model-constraint DDL
  outside the adapter macro; v2 needs the explicit call site.

Verified: cargo check -p dbt-loader clean; cargo test -p dbt-loader --test main:
44 passed, 0 failed (pre-existing suite, unaffected by this change — no test
coverage added here, matching Parts 1-7's precedent of leaving test authorship
to a dedicated pass).

Closes #8