* Add ClickHouse schema collection (collect_schemas)

Adds catalog metadata collection for DBM Schema Explorer: databases,
tables, views, and columns via new ClickhouseMetadata job class.
Introduces collect_schemas config block with include/exclude regex
filters for databases and tables.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* test(clickhouse): remove per-table size gauge test from schema-collection PR

That test checks clickhouse.table.rows/bytes which are emitted by
ClickhouseTableMetrics — a feature in the schema-metrics PR, not here.
Also remove the schema_metrics fixture config that has no effect in this branch.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* fix(clickhouse): rename changelog entry to match PR number 23899

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* test(clickhouse): remove view refresh metric assertions from schema-collection test

clickhouse.view.refresh.status and next_time are emitted by
_collect_view_refresh_metrics(), which lives in the schema-metrics PR.
Keep only the is_refreshable catalog payload assertion here.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* fix(clickhouse): sync CollectSchemas model formatting with spec.yaml

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* fix(clickhouse): validate collect_schemas interval and correct default-off docs

- Normalize collect_schemas.collection_interval in _apply_validated_defaults
  so a 0/negative value is downgraded to the default with a warning instead
  of raising ZeroDivisionError at rate_limit = 1 / collection_interval.
- Fix spec.yaml enabled example (true -> false) and regenerate
  conf.yaml.example so docs match the actual default-off behavior.
- Add regression test for zero/negative collection_interval.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* fix(clickhouse): emit tables and views in a single tables list

Collapse the per-database schema payload to one `tables` list instead of
separate `tables`/`views` arrays, matching the canonical DBM schema shape
used by postgres/mysql/sqlserver (whose backend structs carry only Tables).
Views remain identifiable via the `engine` field (View, MaterializedView,
LiveView, WindowView) and `is_refreshable`.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* fix(clickhouse): bind schema-filter regex patterns as query parameters

User-supplied include/exclude regex patterns were interpolated into the
schema-collection SQL with manual quote-escaping. Bind them as
clickhouse-connect query parameters ({name:String}) instead, eliminating the
SQL-injection surface. Only trusted structural pieces (system-table
identifiers, validated integer limits, the constant system-database list)
remain interpolated.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* Remove redundant int() casts — typed config already guarantees int

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* Remove redundant tuple() and or () guards — defaults applied in config.py

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* Remove redundant collect_schemas null check — always initialized with defaults

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

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Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

* Finalize Agent release 7.79.2

* Apply suggestions from code review

Co-authored-by: Sarah Witt <sarah.witt@datadoghq.com>

---------

Co-authored-by: sarah-witt <33498636+sarah-witt@users.noreply.github.com>
Co-authored-by: Sarah Witt <sarah.witt@datadoghq.com>

* fix kerberos tests

* rename image