docs: drop to_relation() push-side aspiration (bridging is pull-side, remediation D1)

CLAUDE.md

@@ -30,8 +30,8 @@ tests, and this `CLAUDE.md` live in this repo's tree.
 ### Core Components
 
 1. **Protocol layer** (`src/mountainash_data/core/protocol.py`)
-   - `Backend` protocol — what every backend must implement (`connect()`)
-   - `Connection` protocol — what every connection must implement (`list_tables()`, `inspect_table()`, `to_relation()`, `close()`)
+   - `Backend` protocol — the single handle every backend must implement: `connect()`/`close()`/context-manager lifecycle, `list_tables()`/`list_namespaces()`/`list_catalogs()`, and `inspect_table()`/`inspect_namespace()`/`inspect_catalog()`
+   - There is deliberately no `to_relation()` on the protocol — bridging to the unified `mountainash` package is pull-side: `table()` returns a backend-native ibis Table and `ma.relation(ibis_table)` compiles against it directly
 
 2. **Inspection model** (`src/mountainash_data/core/inspection.py`)
    - `CatalogInfo`, `NamespaceInfo`, `TableInfo`, `ColumnInfo` — shared physical metadata dataclasses
@@ -244,7 +244,10 @@ conn = backend.connect()
 try:
     tables = conn.list_tables()
     info = conn.inspect_table("users")
-    relation = conn.to_relation("users")  # → mountainash-expressions Relation
+    ibis_table = conn.table("users")  # backend-native ibis Table
+    # Bridge to the unified mountainash package (pull-side):
+    #   import mountainash as ma
+    #   rel = ma.relation(ibis_table)  # compiles against Ibis automatically
 finally:
     conn.close()
 

README.md

@@ -44,7 +44,10 @@ conn = backend.connect()
 try:
     tables = conn.list_tables()
     info = conn.inspect_table("my_table")
-    relation = conn.to_relation("my_table")  # → mountainash-expressions Relation
+    ibis_table = conn.table("my_table")  # backend-native ibis Table
+    # Bridge to the unified mountainash package (pull-side):
+    #   import mountainash as ma
+    #   rel = ma.relation(ibis_table)  # compiles against Ibis automatically
 finally:
     conn.close()
 
@@ -129,7 +132,7 @@ from mountainash_data import (
 
 - **12-dialect ibis registry** — SQLite, DuckDB, MotherDuck, PostgreSQL, MySQL, MSSQL, Oracle, Snowflake, BigQuery, Redshift, Trino, PySpark
 - **Protocol-first design** — `Backend` and `Connection` protocols enable type-safe composition
-- **Expressions seam** — `Connection.to_relation()` bridges to `mountainash-expressions`
+- **mountainash seam (pull-side)** — `table()` returns a backend-native ibis Table; `ma.relation(table)` in the unified `mountainash` package compiles against it directly. There is deliberately no push-side `to_relation()` bridge in this package.
 - **Settings-driven** — pydantic settings for every dialect, factory auto-detection from URLs
 - **Comprehensive test suite** ensuring reliability
 

src/mountainash_data/backends/iceberg/connection.py

@@ -13,9 +13,11 @@
 - Schema caching
 - Thin delegation wrappers to ``operations.py`` for all mutations
 
-``to_relation()`` is intentionally NOT implemented — it requires
-mountainash-expressions to gain an Iceberg adapter, which is a separate
-work item tracked in the spec.
+There is deliberately no ``to_relation()`` here (or anywhere in this
+package): bridging to the unified ``mountainash`` package is pull-side —
+``ma.relation(...)`` over a backend-native handle. For Iceberg that handle
+is not an ibis Table; reaching mountainash goes via an Arrow scan of the
+loaded ``table()``, or via an Ibis engine reading the catalog.
 """
 
 from __future__ import annotations