Add PatchSizeHelper and guard against fast-buffer allocations

[Cryotechnic]

• Introduce PatchSizeHelper to centralize int32-safety checks and fast-buffer eligibility (CanUseFastBuffer, ToCheckedInt32).
• PatchCoreFastBuffer now validates sizes and uses checked conversions when renting/allocating buffers and reading streams, and falls back to the streaming patch core if requirements are exceeded.
• PatchDir and PatchSingle were refactored to create the appropriate IPatchCore via CreatePatchCore, using PatchSizeHelper to decide between fast-buffer and streaming cores and to log when falling back.
• Adjusted memory rounding logic and cover buffer sizing to avoid int overflows.

[sentry]

Bug: Streams are disposed twice, once in the core patching logic and again in the calling methods, which will cause an ObjectDisposedException.
_{Severity: HIGH}

Suggested Fix

The responsibility for disposing streams should be handled in only one place. Remove the Dispose() calls for clips, inputStream, and outputStream from within PatchCore.WriteCoverStreamToOutput and PatchCoreFastBuffer.WriteCoverStreamToOutputFast. Let the calling methods in PatchDir and PatchSingle manage the lifecycle of the streams they create.

Prompt for AI Agent

Review the code at the location below. A potential bug has been identified by an AI
agent. Verify if this is a real issue. If it is, propose a fix; if not, explain why it's
not valid.

Location: SharpHDiffPatch.Core/Patch/PatchCoreFastBuffer.cs#L39-L44

Potential issue: The `UncoverBufferClipsStream` method, whether using the fast path or
the standard implementation, disposes the `clips`, `inputStream`, and `outputStream`
objects. The calling methods, `PatchDir.StartPatchRoutine` and
`PatchSingle.StartPatchRoutine`, also dispose these same streams in their `finally`
blocks. This guarantees that `Dispose()` will be called twice on the same stream objects
in all execution paths. This will cause an `ObjectDisposedException` when the second
disposal is attempted, leading to a failure in the patching operation.

Also affects:

• SharpHDiffPatch.Core/Patch/PatchDir.cs:169~190
• SharpHDiffPatch.Core/Patch/PatchSingle.cs:29~51

_{Did we get this right? 👍 / 👎 to inform future reviews.}