fix: bolt optimization push node kind filtering to sqlite in keyword fallback search

[n24q02m]

What

Optimized the semantic_search_nodes keyword fallback logic to push the kind filtering down to the SQLite search_nodes query.

Why

Previously, store.search_nodes was called without the kind parameter, meaning all matched nodes were materialized into Python memory, and then filtered by kind. If the initial result set (constrained by limit * 2) was saturated with nodes of the wrong kind, the subsequent Python-side filtering could result in truncating valid matches, returning far fewer results (or zero).

Impact

• Correctness: Valid search results are no longer incorrectly truncated by applying the limit before filtering.
• Performance: Avoids Python-side materialization of unnecessary database rows, preventing unnecessary Python object creation and memory overhead during search.

Measurement

• The kind parameter is now passed directly into the query, applying the AND kind = ? (via the existing _kind_filter) logic in SQLite before returning limited rows.
• Verified that tests (uv run pytest) and linters (uv run ruff check) still pass cleanly.

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PR created automatically by Jules for task 6804011392438315513 started by @n24q02m

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[github-actions]

Dependency Review

✅ No vulnerabilities or license issues or OpenSSF Scorecard issues found.

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