[Perf] Behavior-preserving hot-path allocation/LINQ wins (#264)

* [Perf] Gate event-flag tracing so it allocates nothing when disabled

TraceEventFlag built its interpolated argument (and, on the wait path,
FormatFrameChain + a new StringBuilder(256) in FormatGuestWaitObject plus
~12 guest-memory reads) on every call, then checked the env var inside the
method — so every sceKernelSetEventFlag/Clear/Poll/Wait paid a string
allocation and an Environment.GetEnvironmentVariable P/Invoke even with
tracing off. Cache the flag once in a static readonly bool and gate every
call site, matching the semaphore/event-queue pattern. Behavior is
unchanged when SHARPEMU_LOG_EVENT_FLAG=1.

* [Perf] Hoist IsNoBlockLeaf classification to import-stub setup

The leaf-dispatch path called IsNoBlockLeafImport(nid) — a ~30-literal
string pattern match — on every leaf import. IsLeaf/NidHash were already
precomputed on ImportStubEntry at stub setup; add IsNoBlockLeaf alongside
them and read the field in the hot path. Behavior unchanged.

* [Perf] Cache trace env-var flags read on hot paths

Two SHARPEMU_LOG_* env vars were read via Environment.GetEnvironmentVariable
(a P/Invoke + transient string) on hot paths: SHARPEMU_LOG_FIBER on every
fiber context transfer, and SHARPEMU_LOG_DIRECT_MEMORY on every direct-memory
op (~8 sites). Cache both once — _logFiber alongside the other backend _log*
flags, and _traceDirectMemory behind the existing ShouldTraceDirectMemory
helper. Behavior unchanged.

* [Perf] Avoid per-iteration thread snapshot in the idle pump loop

PumpUntilGuestThreadsIdle allocated a full GuestThreadState[] snapshot
(via LINQ Values.ToArray()) on every spin just to tally three run-state
booleans. Tally them under the lock with an allocation-free helper, and
only materialize the snapshot inside the gated (default-off) diagnostic
dump. SnapshotGuestThreads now uses Values.CopyTo instead of LINQ.
Behavior unchanged.

* [Perf] De-LINQ GetPixelColorExportMask on the per-draw path

GetPixelColorExportMask ran a Select/OfType/Where/Aggregate chain over all
shader instructions, allocating iterators + closures, and is called per
render target (twice per draw via CreateRenderState and HasPixelColorExport).
Replace with a manual scan producing the identical mask — no allocation, and
it removes an authored-LINQ use the repo bans.

* [Perf] De-LINQ per-draw render-target selection in AgcExports

The bound-render-target selection used Where(...).OrderBy(...).ToArray()
(plus a second Where/ToArray fallback) on every translated draw, allocating
LINQ iterators + closures. Replace with an explicit filter into a pre-sized
list + List.Sort by slot; slots are distinct so this matches the stable
OrderBy. Same result, no per-draw LINQ allocations.

* [Perf] De-LINQ per-draw render-target validation in the Vulkan presenter

SubmitOffscreenTranslatedDraw validated its render targets with
targets.Any(...) twice plus targets.Select(a=>a.Address).Distinct().Count()
(a per-draw HashSet), and broadcast a single blend with
Enumerable.Repeat(...).ToArray(). Targets are <= 8, so replace with manual
scans (invalid-target check; combined dimension-mismatch + pairwise
aliasing check) and Array.Fill. Same results, no per-draw LINQ allocations.

* [Perf] Binary-search VirtualQuery region lookup (SortedList)

_mappedRegions was an unordered Dictionary, so TryFindVirtualQueryRegionLocked
scanned every region for containment/next — O(n) per sceKernelVirtualQuery and
O(n^2) when an allocator walks the address space with the findNext flag. Store
regions in a SortedList keyed by base address (every write already uses the
region's own address as the key) and find the containing/next region with a
binary search over the sorted keys. Also drops a now-redundant Values.OrderBy.

Non-overlapping regions assumed (mmap semantics), so only the floor region can
contain the query. Behavior-preserving; worth spot-checking VirtualQuery-heavy
titles.

* [Perf] Remove stray CLI packages.lock.json committed by mistake

git add -A in an earlier commit swept in a regenerated
src/SharpEmu.CLI/packages.lock.json. main tracks no lock files (central
package management, no RestorePackagesWithLockFile), and REUSE.toml no
longer covers packages.lock.json, so the committed file failed the REUSE
Compliance check. Remove it.

src/SharpEmu.Core/Cpu/Native/DirectExecutionBackend.Imports.cs

@@ -598,7 +598,7 @@ public sealed partial class DirectExecutionBackend
 				}
 
 				*(ulong*)(argPackPtr + 96) = unchecked((ulong)transferStub);
-				if (string.Equals(Environment.GetEnvironmentVariable("SHARPEMU_LOG_FIBER"), "1", StringComparison.Ordinal))
+				if (_logFiber)
 				{
 					Console.Error.WriteLine(
 						$"[LOADER][TRACE] fiber.context-transfer rip=0x{transferTarget.Rip:X16} " +
@@ -1292,7 +1292,7 @@ public sealed partial class DirectExecutionBackend
 		}
 
 		int returnValue;
-		if (IsNoBlockLeafImport(importStubEntry.Nid))
+		if (importStubEntry.IsNoBlockLeaf)
 		{
 			cpuContext.ClearRaxWriteFlag();
 			returnValue = export.Function(cpuContext);