feat(query): support indexes on materialized views

[TCeason]

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Summary

• Support CREATE and DROP for inverted, NGRAM, vector, and spatial indexes on non-aggregating materialized views.
• Only synchronous index creation is supported.
• Build synchronous index files for blocks written by REFRESH MATERIALIZED VIEW.
• Existing materialized view blocks are not backfilled.
• Explicit REFRESH ... INDEX ... ON materialized views and index read paths remain out of scope.

Rejected Cases

Asynchronous indexes

  CREATE ASYNC INVERTED INDEX idx ON mv(content); -- rejected

Aggregating materialized views

  CREATE MATERIALIZED VIEW mv_agg (content, row_count) AS
    SELECT content, COUNT(*)
    FROM source
    GROUP BY content;

  CREATE INVERTED INDEX idx ON mv_agg(content); -- rejected

Internal materialized view columns

  CREATE INVERTED INDEX idx ON mv(_mv_source_row_id); -- rejected

Tests

• Unit Test
• Logic Test
• Benchmark Test
• No Test - Explain why

Type of change

• Bug Fix (non-breaking change which fixes an issue)
• New Feature (non-breaking change which adds functionality)
• Breaking Change (fix or feature that could cause existing functionality not to work as expected)
• Documentation Update
• Refactoring
• Performance Improvement
• Other (please describe):

AI assistance

• AI usage: AI generated the base code, and I reviewed the diff.
• Responsible human: @TCeason
• The responsible human has read every line of this diff and can explain each change

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