Wire wait stats config as single source of truth (#215 part 2)

[erikdarlingdata]

Part 2 of #215. Wires the JSON config from Part 1 (#296) into the analysis pipeline so it actually drives behavior, then collapses the parallel C# data files into the single source of truth.

Changes

WaitStats.json

• Trim 52 → 44 entries: drop server-level / instance-level waits (THREADPOOL, BACKUPIO, BACKUPBUFFER, HADR_SYNC_COMMIT, DBMIRROR_DBM_EVENT, SQLTRACE_BUFFER_FLUSH) and connection-setup preemptive waits (PREEMPTIVE_OS_AUTHENTICATIONOPS, PREEMPTIVE_OS_LOOKUPACCOUNTSID) — none of these appear in plan XML's <WaitStats> element. Per @jobbish-sql's feedback on Seed wait stats config file (#215 part 1) #296.
• Populate attributes 6–8 from existing tool behavior:
  • showWaitCount: true everywhere (matches current ShowWaitStats always rendering "(N waits)")
  • showAverageWaitTime: true for PAGEIOLATCH_SH/EX/UP/DT (the four entries WaitStatsKnowledge.ShowEffectiveLatency=true was set on); false elsewhere
  • timeCalculationModel: "cpu time based" for isExternal=true (4 PREEMPTIVE_* + MEMORY_ALLOCATION_EXT); "direct" for RESOURCE_SEMAPHORE and ASYNC_NETWORK_IO (Joe's explicit examples); "elapsed time based" for the remaining 37 entries (his stated default)
• Attributes 9–12 (applicable operators, descriptions, URLs, internal comment) intentionally remain null — those need domain expertise.

WaitStatsConfig (new)

• PlanViewer.Core.Services.WaitStatsConfig loads the JSON from an embedded resource on first access, caches by name (case-insensitive Dictionary).
• Resource lookup is suffix-based (EndsWith("Resources.WaitStats.json")) so the file works whether embedded under PlanViewer.Core.* or PlanViewer.Web.* manifest prefixes (Web project compiles linked Core sources into its own assembly).
• Public surface: Get(name), IsExternal(name), ShowAverageWaitTime(name). Lookup misses return null / false, preserving prior defaults for unknown waits.

Code wiring

• BenefitScorer.IsExternalWait now delegates to WaitStatsConfig.IsExternal.
• BenefitScorer.EmitWaitStatWarnings drops the WaitStatsKnowledge.Lookup dependency and reads ShowAverageWaitTime from the config.
• WaitStatsKnowledge.cs deleted — its only structural data (ShowEffectiveLatency) is now sourced from the config; Description and HowToFix were intentionally empty since [FEATURE] Add system to assign a "maximum benefit" for plan analysis rules #215 D3, so nothing of substance is lost.

Project files

• PlanViewer.Core.csproj: add Resources/WaitStats.json as <EmbeddedResource>.
• PlanViewer.Web.csproj: replace the linked WaitStatsKnowledge.cs with WaitStatsConfig.cs; add a linked <EmbeddedResource> for the JSON so the WebAssembly assembly carries its own copy.

Test plan

• dotnet build clean for Core, App, and Web (4 pre-existing AVLN3001 warnings in App, unrelated)
• dotnet test — 75/75 Core tests pass
• Smoke-test in app: open a .sqlplan with PAGEIOLATCH_SH waits and verify the warning still includes "Effective latency: ... per wait"
• Smoke-test in app: open a .sqlplan with PREEMPTIVE_* or MEMORY_ALLOCATION_EXT waits and verify the CPU-based external-wait benefit % still calculates

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