* docs: add view groups documentation

Add documentation for the view_group feature introduced in v1.6.43:

- New reference page: reference/data-modeling/view-group.mdx
  Covers name, title, description, and views parameters with
  YAML and JavaScript examples using the ecommerce data model.

- View reference: add view_group and view_groups parameters
  Documents both singular and plural forms for assigning views
  to groups.

- Conceptual views page: add 'Grouping views with view groups'
  section with a full example showing both group-level and
  view-level assignment.

- Syntax page: mention view_groups in folder structure example.

- Navigation: add view-group page to Reference > Data Modeling.

Co-authored-by: Pavel Tiunov <pavel.tiunov@gmail.com>

* docs: use underscore notation consistently in JS examples

Replace viewGroup/viewGroups with view_group/view_groups in JavaScript
code examples to follow the Cube DSL convention of snake_case across
all syntaxes (YAML and JavaScript).

Co-authored-by: Pavel Tiunov <pavel.tiunov@gmail.com>

* fix

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Co-authored-by: Cursor Agent <cursoragent@cursor.com>
Co-authored-by: Artyom Keydunov <artyom.keydunov@gmail.com>

…10824)

The event has passed; remove the promo banner from docs.

Co-authored-by: Cursor <cursoragent@cursor.com>

…he (#10822)

* feat(cubestore): add stale-while-revalidate timeout for SQL query cache

Add CUBESTORE_QUERY_CACHE_STALE_WHILE_REVALIDATE env config param that
enables stale-while-revalidate behavior for CubeStore's SQL result cache.

When enabled (set to a number of seconds, e.g. 30), the cache maintains
a secondary lookup keyed only by SQL query text + inline tables (ignoring
partition/chunk IDs). If a query arrives and the exact cache key (which
includes current partition/chunk snapshot) misses, but a stale entry
exists and was created within the configured timeout, the stale result is
served immediately while a background task refreshes the cache with fresh
data.

This is disabled by default (0 = disabled). The feature reduces query
latency during compaction or partition changes when the underlying data
hasn't materially changed.

Changes:
- config/mod.rs: Add query_cache_stale_while_revalidate_secs to ConfigObj
  trait and ConfigObjImpl, parsed from CUBESTORE_QUERY_CACHE_STALE_WHILE_REVALIDATE
- sql/cache.rs: Add stale_cache (Moka cache keyed by SqlQueueCacheKey),
  stale-while-revalidate lookup in get(), background refresh via tokio::spawn
- app_metrics.rs: Add DATA_QUERIES_CACHE_STALE_HIT counter metric
- Unit test for stale-while-revalidate behavior

Co-authored-by: Pavel Tiunov <pavel.tiunov@gmail.com>

* refactor(cubestore): use queue cache for background stale-while-revalidate refresh

The background refresh spawned by stale-while-revalidate now integrates
with the queue cache dedup mechanism:

- Extract try_register_background() which atomically checks if a query is
  already in flight in the queue cache and registers a new entry if not.
- On stale hit, try_register_background() is called first. If another
  execution is already in flight (from a previous stale hit or a
  concurrent foreground request), we skip spawning entirely.
- The background spawn registers a watch::Sender in the queue cache, so
  any concurrent foreground get() for the same SQL that doesn't hit the
  stale cache will join as a waiter instead of starting a duplicate
  execution.
- Queue cache entry cleanup happens lazily: sender is dropped when the
  background task completes, closing the channel. The next get() for that
  key detects the closed channel via has_changed().is_err() and pops it.

Co-authored-by: Pavel Tiunov <pavel.tiunov@gmail.com>

* refactor(cubestore): reuse queue cache flow for background stale-while-revalidate

Extract get_inner() with is_background_refresh flag from get(). The
background spawn now calls get_inner(true) which skips the stale cache
check but reuses the entire queue cache dedup flow — no separate
implementation for the background path.

- get() is a thin wrapper: delegates to get_inner(false)
- get_inner(is_background_refresh=true) skips stale check, goes
  straight to queue cache logic for natural dedup
- get() now takes self: &Arc<Self> so the spawn can clone the Arc
- get_inner() takes self: Arc<Self> and returns Pin<Box<dyn Future>>
  to satisfy Send + 'static bounds for tokio::spawn
- Removed try_register_background() and all duplicated cache update
  logic from previous approach

Co-authored-by: Pavel Tiunov <pavel.tiunov@gmail.com>

* fix(cubestore): fix stale-while-revalidate test to simulate partition change

The test now invalidates the exact result cache before the second get()
call to simulate a partition/chunk change that would make the exact cache
key miss while the stale entry (keyed by SQL only) still matches.

Co-authored-by: Pavel Tiunov <pavel.tiunov@gmail.com>

* fix(cubestore): address review feedback on stale-while-revalidate cache

- Add weigher to stale_cache so max_capacity is in bytes, not entry count
- Fix clippy: use Duration::from_secs as method reference instead of closure
- Add test: background refresh failure preserves stale entry for next request
- Add test: stale timeout expiry falls through to fresh execution

Co-authored-by: Pavel Tiunov <pavel.tiunov@gmail.com>

* feat(cubestore): add size/weight metrics for stale cache

Add cs.sql.query.data.cache.stale.size and cs.sql.query.data.cache.stale.weight
gauge metrics mirroring the existing result cache metrics. Reported alongside
result cache metrics on cache mutations and zeroed on drop.

Co-authored-by: Pavel Tiunov <pavel.tiunov@gmail.com>

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Co-authored-by: Cursor Agent <cursoragent@cursor.com>