Thread cancellation through 10 Alerts/MemoryGrants/Health web reads (#4203)

[erikdarlingdata]

Refs #4203.

Why

Per #4203, web reads should honour request cancellation so an abandoned /api/read request stops its store query instead of running to completion. #4357 and #4359 did this for the Performance-Trends tools; this slice does the same for every allowlisted tool defined in DarlingMcpAlertTools.cs, DarlingMcpMemoryGrantTools.cs and DarlingMcpHealthTools.cs.

What changes

Ten tools now take a trailing CancellationToken cancellationToken = default, pass it to every store call in their bodies, narrow their catch to when (ex is not OperationCanceledException), and are removed from CancellationAllowlist; their dispatch entries now pass cancellationToken: c.RequestAborted:

• get_alert_history
• get_alert_settings
• get_mute_rules
• get_notification_routes
• get_resource_semaphore
• get_memory_grants
• get_memory_pressure_events
• get_server_summary
• get_daily_summary
• get_daily_summary_range

get_mute_rules's store call (PgMuteRuleStore.LoadAllAsync) required a shared-interface change: IMuteRuleStore.LoadAllAsync gained a CancellationToken cancellationToken = default parameter. Every implementation was updated to match: PgMuteRuleStore (now uses it on the connection open/reader), DuckDbMuteRuleStore (Lite, param added, not yet wired to the DuckDB calls — Lite has no cancellable read path here, kept as the smallest change), and the deprecated JsonMuteRuleStore (Dashboard, synchronous, param added for compile parity only). Test fakes (Darling.Tests/MuteRuleReloadRetentionTests.cs's ScriptedMuteRuleStore, Darling.Tests/DarlingMcpAlertToolsTests.cs's FakeMuteRuleStore, Lite.Tests/RemainingEmptyReadsToolTests.cs's InMemoryMuteRuleStore, Lite.Tests/MuteRuleServiceTests.cs's FakeMuteRuleStore) all had the same parameter added to their overrides so every other caller of LoadAllAsync() (the write-verb tools create_mute_rule, delete_mute_rule, set_mute_rule_enabled, update_mute_rule — none of them allowlisted, out of this slice's scope) still compiles unchanged against the new default parameter.

set_notification_route_enabled and delete_notification_route (write verbs) and create_mute_rule/delete_mute_rule/set_mute_rule_enabled/update_mute_rule (write verbs) were left untouched: none were in CancellationAllowlist to begin with, so they're out of this slice's scope per the brief.

Test plan

• dotnet build Darling/Darling.Tests/Darling.Tests.csproj -p:EnableWindowsTargeting=true: 0 warnings, 0 errors.
• dotnet build Lite.Tests/Lite.Tests.csproj -p:EnableWindowsTargeting=true: 0 warnings, 0 errors.
• The existing WebReadCancellationPinTests (EveryStoreReadingToolMethod_TakesACancellationToken_UnlessAllowlisted, CancellationAllowlist_HasNoStaleEntry) is a reflection ratchet: removing these ten names from the allowlist makes it enforce them going forward. RED case before this change: any of the ten dispatch entries invoked its tool without threading c.RequestAborted, so a cancelled request's underlying store call ran to completion — the pin's EveryStoreReadingToolMethod_TakesACancellationToken_UnlessAllowlisted check would fail once the name left the allowlist while the method still lacked the parameter (the actual RED state on the pre-fix code, since the allowlist entry was masking the check).
• Darling.Tests and Lite.Tests target net10.0-windows: they build here but cannot run on macOS — listed unchecked; CI decides them.

CHANGELOG entry

SECTION: Fixed
ENTRY:

• Web reads honour request cancellation for Alerts, Memory Grants and Health MCP tools ([Thread cancellation through 10 Alerts/MemoryGrants/Health web reads (#4203) #4386]) - get_alert_history, get_alert_settings, get_mute_rules, get_notification_routes, get_resource_semaphore, get_memory_grants, get_memory_pressure_events, get_server_summary, get_daily_summary and get_daily_summary_range previously ran their store query to completion even after an abandoned web request; they now take a CancellationToken and pass it through every store call.
  REF:
  [Thread cancellation through 10 Alerts/MemoryGrants/Health web reads (#4203) #4386]: Thread cancellation through 10 Alerts/MemoryGrants/Health web reads (#4203) #4386