* feat(tools): add Serply as a web_search provider
Serply is a SERP API returning Google web results on a tenant-supplied
key. It joins the existing chain the same way Exa, Tavily and Brave do:
keyed from config_secrets, skipped silently when no key is stored, and
selectable through the provider parameter for cross-engine corroboration.
Freshness maps onto Google's tbs recency filter, which Serply forwards
upstream. Only the pd/pw/pm/py shortcuts are sent: upstream ignores the
equivalent cdr date range and answers with unfiltered results, so a
range leaves tbs unset rather than naming a filter the results do not
honour.
The settings form gained a fifth sortable provider, so the locked
DuckDuckGo card now derives its position number instead of hardcoding
it, and a stored provider_order is reconciled against the full provider
list rather than against Parallel alone.
* test(tools): use a locally named round trip stub in the serply test
The serply cancellation test borrowed parallelRoundTripFunc from
web_search_parallel_test.go. Define serplyRoundTripFunc alongside the
test that uses it so the file does not depend on another provider's
test helper.
Refactor WebSearchTool constructor to accept ConfigSecretsStore and
MessageBus instead of hardcoded WebSearchConfig. Implement runtime
per-tenant provider chain resolution via tenantChainCache.
Constructor now:
- Subscribes to cache invalidation events on config_secrets changes
- Returns nil-safe tool instance (no early return on empty providers)
- Passes secrets store and bus for dynamic resolution per Execute() call
Add resolve unit tests; delete legacy config_test.go (functionality
subsumed by cache tests and integration tests).
Serply