PDF follow-ups: import layers, arcs and joins, names, background, page placement, snaps

- Unlayered raster images go with the PDF layer drawn last before them.
- Circular Bezier arcs import as arcs: bulged polyline segments with Join,
  ARC entities without it; straight chains still join.
- Imported PNGs go to "PDF Images" next to the PDF; import blocks are
  numbered imp31, imp32, ...
- Background darkness is its HSL lightness below one half.
- All chosen pages attach at the same insertion point.
- PDF geometry snaps as separate pieces: centre from the rim, intersections
  and perpendiculars.
- Automation: snap query with an optional base point.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/mcp.rs

@@ -35,6 +35,7 @@ const READ_OPS: &[&str] = &[
     "header",
     "properties",
     "measure",
+    "snap",
     "history",
     "commands",
     "events",
@@ -1198,7 +1199,7 @@ fn tool_definitions() -> Value {
         {
             "name":"ocs_read",
             "description":"Discover capabilities and record schemas, or read state, complete database records, command manifests, entities, properties, kernel measurements and spatial relationships, history, events or operation status from a live OCS session.",
-            "inputSchema":{"type":"object","properties":{"ocs_session_id":{"type":"string","minLength":1,"description":"Value of session_id returned by ocs_sessions."},"op":{"type":"string","enum":READ_OPS,"default":"state"},"parameters":{"type":"object","description":"Operation-specific filters.","properties":{"name":{"type":"string","description":"Command name or record name."},"search":{"type":"string","description":"Case-insensitive command or record-type search."},"document_id":{"type":"integer","minimum":0},"path":{"type":"string","description":"Optional intended output path for audit; extension determines target format."},"target_format":{"type":"string","enum":["dwg","dxf"],"description":"Intended output format for audit."},"target_version":{"type":"string","enum":["R14","2000","2004","2007","2010","2013","2018","AC1014","AC1015","AC1018","AC1021","AC1024","AC1027","AC1032"],"description":"Intended CAD output version for audit."},"collection":{"type":"string","description":"Record collection, all for records, or omit to discover collections and schema types."},"handle":{"type":"string"},"handles":{"type":"array","items":{"type":"string"},"description":"Exact entity or record handles."},"type":{"type":"string","description":"Entity or record type filter; for record_schema, returns its complete type graph and writable field paths."},"layer":{"type":"string","description":"Layer name filter for query."},"detail":{"type":"string","enum":["summary","geometry","full"],"default":"geometry","description":"Entity detail returned by query."},"fields":{"type":"array","items":{"type":"string"},"description":"Return only these entity fields plus handle."},"paths":{"type":"array","items":{"type":"string"},"description":"Project RFC 6901 JSON Pointer paths relative to record.properties."},"where":{"type":"array","description":"All property filters must match.","items":{"type":"object","properties":{"path":{"type":"string"},"op":{"type":"string","enum":["eq","ne","lt","lte","gt","gte","contains","starts_with","ends_with","in","exists","not_exists"],"default":"eq"},"value":{}},"required":["path"],"additionalProperties":false}},"near":{"type":"array","items":{"type":"number"},"minItems":2,"maxItems":3,"description":"Rank planar curves by exact kernel distance to this world XY point."},"contains_point":{"type":"array","items":{"type":"number"},"minItems":2,"maxItems":3,"description":"Return closed planar curves containing this world XY point."},"bounds":{"type":"array","items":{"type":"number"},"minItems":4,"maxItems":4,"description":"Filter entities whose world XY bounds overlap [min_x,min_y,max_x,max_y]."},"intersections":{"type":"array","items":{"type":"string"},"minItems":2,"maxItems":2,"description":"Return exact kernel intersections between two planar curve handles."},"after":{"type":"integer","minimum":0,"description":"Event cursor."},"request_id":{"type":"string","description":"Operation id to query."},"offset":{"type":"integer","minimum":0},"limit":{"type":"integer","minimum":1,"maximum":10000}},"additionalProperties":false}},"required":["ocs_session_id"],"additionalProperties":false},
+            "inputSchema":{"type":"object","properties":{"ocs_session_id":{"type":"string","minLength":1,"description":"Value of session_id returned by ocs_sessions."},"op":{"type":"string","enum":READ_OPS,"default":"state"},"parameters":{"type":"object","description":"Operation-specific filters.","properties":{"name":{"type":"string","description":"Command name or record name."},"search":{"type":"string","description":"Case-insensitive command or record-type search."},"document_id":{"type":"integer","minimum":0},"path":{"type":"string","description":"Optional intended output path for audit; extension determines target format."},"target_format":{"type":"string","enum":["dwg","dxf"],"description":"Intended output format for audit."},"target_version":{"type":"string","enum":["R14","2000","2004","2007","2010","2013","2018","AC1014","AC1015","AC1018","AC1021","AC1024","AC1027","AC1032"],"description":"Intended CAD output version for audit."},"collection":{"type":"string","description":"Record collection, all for records, or omit to discover collections and schema types."},"handle":{"type":"string"},"handles":{"type":"array","items":{"type":"string"},"description":"Exact entity or record handles."},"type":{"type":"string","description":"Entity or record type filter; for record_schema, returns its complete type graph and writable field paths."},"layer":{"type":"string","description":"Layer name filter for query."},"detail":{"type":"string","enum":["summary","geometry","full"],"default":"geometry","description":"Entity detail returned by query."},"fields":{"type":"array","items":{"type":"string"},"description":"Return only these entity fields plus handle."},"paths":{"type":"array","items":{"type":"string"},"description":"Project RFC 6901 JSON Pointer paths relative to record.properties."},"where":{"type":"array","description":"All property filters must match.","items":{"type":"object","properties":{"path":{"type":"string"},"op":{"type":"string","enum":["eq","ne","lt","lte","gt","gte","contains","starts_with","ends_with","in","exists","not_exists"],"default":"eq"},"value":{}},"required":["path"],"additionalProperties":false}},"near":{"type":"array","items":{"type":"number"},"minItems":2,"maxItems":3,"description":"Rank planar curves by exact kernel distance to this world XY point."},"point":{"type":"array","items":{"type":"number"},"minItems":2,"maxItems":3,"description":"World point whose object snap the snap op reports."},"from":{"type":"array","items":{"type":"number"},"minItems":2,"maxItems":3,"description":"Base point for perpendicular and tangent snaps (snap op)."},"contains_point":{"type":"array","items":{"type":"number"},"minItems":2,"maxItems":3,"description":"Return closed planar curves containing this world XY point."},"bounds":{"type":"array","items":{"type":"number"},"minItems":4,"maxItems":4,"description":"Filter entities whose world XY bounds overlap [min_x,min_y,max_x,max_y]."},"intersections":{"type":"array","items":{"type":"string"},"minItems":2,"maxItems":2,"description":"Return exact kernel intersections between two planar curve handles."},"after":{"type":"integer","minimum":0,"description":"Event cursor."},"request_id":{"type":"string","description":"Operation id to query."},"offset":{"type":"integer","minimum":0},"limit":{"type":"integer","minimum":1,"maximum":10000}},"additionalProperties":false}},"required":["ocs_session_id"],"additionalProperties":false},
             "outputSchema":read_output_schema(),
             "annotations":{"title":"Read OCS state","readOnlyHint":true,"destructiveHint":false,"idempotentHint":true,"openWorldHint":false}
         },