fix(google_ads): honor LIMIT in handler select()

[gabrielbressan-tfy]

Problem

SELECT * FROM google_ads_….campaigns LIMIT 3 returns the entire account (3553 campaigns, 192952 keywords, …) instead of 3 rows.

Root cause: for class_type = "api" handlers, plan_api_db_select forwards LIMIT to the handler (query2.limit) and clears it from the outer SubSelectStep (query_planner.py:446). So DuckDB never applies LIMIT — the handler is solely responsible, and the Google Ads handler ignored query.limit entirely.

The report tables (campaign_performance, search_terms) only appeared to honor LIMIT because they returned 0 rows due to the empty default date range, not because LIMIT worked.

Fix

Three helpers added to google_ads_tables.py, wired into all 11 table classes:

• _limit_value(query) — extracts the LIMIT integer.
• _all_conditions_pushable(conditions, col_map) — true only when every WHERE condition is pushed to GAQL.
• _finalize(query, df, columns, can_limit) — selects columns and slices df.head(n) when safe.

Each table now pushes LIMIT n into the GAQL query (so the API returns ≤ n rows instead of the whole account) and slices the DataFrame — but only when the WHERE is fully handled:

• GAQL tables: all conditions pushed down.
• Cached languages / geo_targets: no WHERE.
• Keyword-planner tables: no leftover conditions beyond consumed params.

This gates against under-returning: a complex WHERE (e.g. name LIKE '%a%') that DuckDB re-filters afterward leaves LIMIT off, so we never hand DuckDB fewer rows than it needs.

Validation

Exercised select() with a mocked Google Ads service (remote server has the connector but the local container does not):

case	result
limit 3	GAQL gets LIMIT 3, returns 3 ✅
where status='ENABLED' limit 2	pushed, returns 2 ✅
where name like '%a%' limit 2	not pushed/sliced, full set → DuckDB ✅
no limit	unchanged ✅

🤖 Generated with Claude Code