feat(ogar-adapter-surrealql): AST -> Class walk (closes ADR-017)

The `parse_surrealql_ddl` function now actually walks the SurrealDB
AST and lifts the supported DDL subset into `Vec<Class>`. PR #24
wired the parser for syntax validation only; this PR completes the
walk for the v1 subset.

# Supported in this walk

  - DEFINE TABLE <name>                              -> Class
  - DEFINE FIELD <field> ON <table> TYPE
       string | int | bool | datetime | float | decimal |
       uuid | bytes | object | duration | any            -> Attribute
  - DEFINE FIELD <field> ON <table> TYPE record<X>   -> Association(BelongsTo)
  - DEFINE FIELD <field> ON <table> TYPE option<record<X>>
                                                     -> Association(BelongsTo, optional=true)
  - DEFINE FIELD <field> ON <table> TYPE option<<primitive>>
                                                     -> Attribute(type=option<primitive>)
  - Implicit-table-from-field (no preceding DEFINE TABLE) — the
    walker creates the class lazily on first field encounter.
  - Multi-table definition order preserved.

# Not yet supported (intentional next-sprint shape)

  - DEFINE FIELD … ASSERT $value IN [...]  (EnumDecl::Static lift)
  - VALUE / DEFAULT / COMPUTED clauses
  - PERMISSIONS / FLEXIBLE / READONLY
  - DEFINE EVENT (lifecycle -> ActionDef)
  - DEFINE INDEX (not part of OGAR IR; ignored)
  - Comment-marker recovery for non-owning sides
    (`-- {table} HasMany {name}` is a SurrealQL comment, invisible
    to the parser; the non-owning side is recoverable from the
    owning side's record<X> in a separate post-pass over the full
    Vec<Class>).

# AST walker architecture

New private `walk` module under `#[cfg(feature = "surrealdb-parser")]`:

  - `walk_query(&Ast, Query) -> Vec<Class>` — entry point.
  - `visit_define(&Ast, NodeId<Expr>, &mut by_name, &mut order)`
    matches on Expr::DefineTable / Expr::DefineField.
  - `expr_to_simple_name(&Ast, NodeId<Expr>) -> Option<String>`
    extracts identifier names from `Expr::Path { start: Ident,
    parts: None }`.
  - `lift_field_type(&Ast, Option<NodeId<Type>>) -> FieldShape`
    classifies the Type AST into Primitive | Record | Untyped |
    Other. Handles the `option<X>` encoding (NodeList<PrimeType>
    prefixed with PrimeType::None — per surrealdb/parser/src/
    parse/kind.rs at T![OPTION]).
  - `iter_node_list<T>(&Ast, NodeListId<T>)` — closure-based
    iterator over the AST's linked-list structure.

# Round-trip tests

8 new tests on top of the 14 pre-existing. The shape:

  walk_minimal_table_produces_class
  walk_table_with_string_attribute
  walk_table_with_belongs_to_record_field
  walk_table_with_optional_belongs_to
  walk_multi_table_preserves_definition_order
  walk_round_trip_simple_class      <- emit then parse, structural eq
  walk_round_trip_belongs_to_association
  walk_implicit_table_from_field_alone
  walk_returns_parse_error_on_invalid_ddl

# Producer of `schema_ddl_hint` (the loop closure)

PR #25 introduced `KnowableFromStore::register(class_identity,
schema_ddl_hint: Option<&str>)` — the registry's "self-describing"
clause. Today every caller passes `None`. This PR makes
`emit_surrealql_ddl(&[class.clone()])` the canonical producer of the
hint, closing the loop that PR #25's docstring named ("Future PRs
can render via ogar-adapter-surrealql::emit_surrealql_ddl"). A
follow-up can wire that call into `register_class_knowable_from`'s
body.

# CI floor extended

`.github/workflows/ci.yml` adds:

    cargo test -p ogar-adapter-surrealql --features surrealdb-parser

The default `cargo test --workspace` step doesn't enable the feature
(the parser dep is heavy and not needed by other workspace members);
this extra step makes the walker tests part of the CI floor. ~30-60s
added to CI; bounded scope (one crate).

# Verification

Local:
  - `cargo test -p ogar-adapter-surrealql --features surrealdb-parser`
    -> 22 passed (14 prior + 8 walker tests).
  - `cargo test --workspace` (default, no feature) -> clean (the
    walker code is behind cfg; the existing parser-off test still
    runs).
  - `cargo check --workspace --all-targets` -> clean.

Closes ADR-017 (the surrealql-AST-to-Class walk) for the v1 subset.

https://claude.ai/code/session_01PBTGaPCSnnt6u3pjXpbLwY

Author: claude

.github/workflows/ci.yml

@@ -30,3 +30,9 @@ jobs:
         run: cargo check --workspace --all-targets
       - name: cargo test --workspace
         run: cargo test --workspace
+      # Exercise the feature-gated surrealql AST walk (lifts DDL ->
+      # Class via the surrealdb-parser fork). Crate-scoped because the
+      # parser dep is heavy and not needed by other workspace members;
+      # gating by feature keeps the default build lean.
+      - name: cargo test -p ogar-adapter-surrealql --features surrealdb-parser
+        run: cargo test -p ogar-adapter-surrealql --features surrealdb-parser