fix(install): accept flat Windows release archives without payload wrapper (#1257)

[skbs-eng]

Fixes #1257

Problem

install.ps1's archive namespace check strictly required codebase-memory-mcp.payload.exe to exist as a separate entry in the release zip. In release builds where codebase-memory-mcp.exe is packaged as a flat standalone binary without a separate *.payload.exe entry (such as the v0.9.0 windows-arm64 and windows-amd64 UI archives), install.ps1 aborted with:
\�rror: unsafe or incomplete release archive: archive must contain exactly one codebase-memory-mcp.payload.exe\

Fix

• Updated install.ps1 archive layout validation to require codebase-memory-mcp.exe, LICENSE, install.ps1, and THIRD_PARTY_NOTICES.md, while allowing codebase-memory-mcp.payload.exe to be optional (0 or 1 instance).
• If codebase-memory-mcp.payload.exe is missing from the extracted archive, install.ps1 stage-copies codebase-memory-mcp.exe to codebase-memory-mcp.payload.exe in the temporary directory prior to executing the launcher installation.
• Updated ests/test_windows_bundle_contract.sh static contract checks to reflect the updated archive bounds.

Validation

• Verified with python contract test script (\ est_windows_bundle_contract.sh).
• Tested \install.ps1\ archive extraction against both 4-file (flat layout) and 5-file (pair layout) zip archives.